As filed with the Securities and Exchange Commission on May 8, 2014March 21, 2018

RegistrationNo. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

TRICO BANCSHARES

(Exact name of registrant as specified in its charter)

63 Constitution Drive

Chico, California 95973

(530) 898-0300

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Richard P. Smith

President and Chief Executive Officer

TriCo Bancshares

63 Constitution Drive

Chico, California 95973

(530) 898-0300

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

With copies to:

Approximate date of commencement of proposed sale of the securities to the public:

As soon as practicable after this registration statement becomes effective and upon completion of the merger.

If the securities being registered on this form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box:  ¨

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

If applicable, place anx in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer)

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer)

CALCULATION OF REGISTRATION FEE

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

Information contained herein is subject to completion or amendment. A registration statement relating to the shares of TriCo Bancshares common stock to be issued in the merger has been filed with the Securities and Exchange Commission. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective. This joint proxy statement/prospectus shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale is not permitted or would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

PRELIMINARY JOINT PROXY STATEMENT/PROSPECTUS

DATED MAY 8, 2014, SUBJECT TO COMPLETION

Dear Shareholders of TriCo Bancshares:

On January 21, 2014, TriCo Bancshares, which we refer to as TriCo, entered into an agreement and plan of merger and reorganization, which we refer to as the merger agreement, to acquire North Valley Bancorp, which we refer to as North Valley, in an all-stock transaction. If the merger agreement is approved and the merger is subsequently completed, North Valley will merge with and into TriCo, with TriCo as the surviving entity.

In the merger, each share of North Valley common stock owned by a North Valley shareholder (including the associated preferred stock purchase rights) will be converted into the right to receive 0.9433 shares of TriCo common stock, which we refer to as the exchange ratio. A North Valley shareholder will receive any whole shares of TriCo common stock such holder is entitled to receive and cash in lieu of any fractional shares of TriCo common stock such holder is entitled to receive.

You should obtain current stock price quotations for TriCo common stock and North Valley common stock. TriCo common stock is traded on the NASDAQ Global Select Market under the symbol “TCBK,” and North Valley common stock is traded on the NASDAQ Global Select Market under the symbol “NOVB.”

We expect the merger to be generally tax free to North Valley shareholders for U.S. federal income tax purposes, except for taxes on cash received by North Valley shareholders in lieu of fractional TriCo shares.

Shareholders of TriCo will vote upon the proposed merger and related matters at TriCo’s annual meeting of shareholders at which TriCo will also vote upon proposals to elect TriCo directors, reapprove the existing performance criteria under the TriCo 2009 equity incentive plan, approve an advisory vote of executive compensation and appoint its independent auditor. North Valley will hold a special meeting of shareholders to consider the proposed merger and related matters. TriCo and North Valley cannot complete the proposed merger unless TriCo’s shareholders vote to approve the merger and approve the issuance of TriCo common stock in connection with the merger. This letter is accompanied by the attached document, which TriCo’s board of directors is providing to solicit your proxy to vote for approval of the merger and the issuance of TriCo common stock in connection with the merger and other matters in connection with its annual meeting.

The accompanying document is also being delivered to North Valley shareholders as TriCo’s prospectus for its offering of TriCo common stock in connection with the merger, and as a proxy statement for the solicitation of proxies from North Valley shareholders to vote to approve the merger.

Your vote is very important. To ensure your representation at the TriCo annual meeting, please complete and return the enclosed proxy card or submit your proxy by telephone or through the Internet. Whether or not you expect to attend the TriCo annual meeting, please vote promptly. Submitting a proxy now will not prevent you from being able to vote in person at the TriCo annual meeting.The TriCo board of directors has unanimously approved the merger agreement and the transactions contemplated thereby and unanimously recommends that you vote:

This document provides you with detailed information about the proposed merger. It also contains or refers to information about TriCo and North Valley and certain related matters. You are encouraged to read this document carefully.In particular, you should read the “Risk Factors” section beginning on page 23 for a discussion of the risks you should consider in evaluating the proposed merger and how it will affect you.

Sincerely,

Richard P. Smith

President and Chief Executive Officer

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the merger, the issuance of the TriCo common stock in connection with the merger or the other transactions described in this document, or passed upon the adequacy or accuracy of the disclosure in this document. Any representation to the contrary is a criminal offense.

The securities to be issued in connection with the merger are not savings accounts, deposits or other obligations of any bank or savings association and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

This document is dated [—], and is first being mailed to shareholders of TriCo and North Valley on or about [—].

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To the Shareholders of North Valley Bancorp:

On January 21, 2014, TriCo Bancshares, which we refer to as TriCo, entered into an agreement and plan of merger and reorganization, which we refer to as the merger agreement, to acquire North Valley Bancorp, which we refer to as North Valley, in an all-stock transaction. If the merger agreement is approved and the merger is subsequently completed, North Valley will merge with and into TriCo, with TriCo as the surviving entity.

In the merger, each share of North Valley common stock owned by a North Valley shareholder (including the associated preferred stock purchase rights) will be converted into the right to receive 0.9433 shares of TriCo common stock, which we refer to as the exchange ratio. A North Valley shareholder will receive any whole shares of TriCo common stock such holder is entitled to receive and cash in lieu of any fractional shares of TriCo common stock such holder is entitled to receive.

You should obtain current stock price quotations for TriCo common stock and North Valley common stock. North Valley common stock is traded on the NASDAQ Global Select Market under the symbol “NOVB” and TriCo common stock is traded on the NASDAQ Global Select Market under the symbol “TCBK.”

We expect the merger to be generally tax free to North Valley shareholders for U.S. federal income tax purposes, except for taxes on cash received by North Valley shareholders in lieu of fractional TriCo shares.

North Valley will hold a special meeting of shareholders to consider the proposed merger and related matters. Shareholders of TriCo will vote upon the proposed merger and related matters at TriCo’s annual meeting of shareholders. TriCo and North Valley cannot complete the proposed merger unless TriCo’s shareholders vote to approve the merger and approve and adopt the merger agreement and approve the issuance of TriCo common stock in connection with the merger. This letter is accompanied by the attached document, which our board of directors is providing to solicit your proxy to vote for approval of the merger and the approval and adoption of the merger agreement.

The accompanying document is also being delivered to North Valley shareholders as TriCo’s prospectus for its offering of TriCo common stock in connection with the merger, and as a proxy statement for the solicitation of proxies from TriCo shareholders to vote for approval of the merger and the approval and adoption of the merger agreement and approval of the issuance of TriCo common stock in connection with the merger.

Your vote is very important. To ensure your representation at the North Valley special meeting, please complete and return the enclosed proxy card or submit your proxy by telephone or through the Internet. Whether or not you expect to attend the North Valley special meeting, please vote promptly. Submitting a proxy now will not prevent you from being able to vote in person at the North Valley special meeting. The North Valley board of directors has unanimously approved the merger agreement and the transactions contemplated thereby and unanimously recommends that you vote “FOR” approval of the merger and approval and adoption of the merger agreement, “FOR” the advisory (non-binding) proposal to approve specified compensation that may become payable to the named executive officers of North Valley in connection with the merger and “FOR” any adjournment of the North Valley special meeting, if necessary or appropriate, including to permit further solicitation of proxies in favor of the preceding votes.

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This document provides you with detailed information about the proposed merger. It also contains or refers to information about North Valley and TriCo and certain related matters. You are encouraged to read this document carefully.In particular, you should read the “Risk Factors” section beginning on page 23 for a discussion of the risks you should consider in evaluating the proposed merger and how it will affect you.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the merger, the issuance of the TriCo common stock in connection with the merger or the other transactions described in this document, or passed upon the adequacy or accuracy of the disclosure in this document. Any representation to the contrary is a criminal offense.

The securities to be issued in connection with the merger are not savings accounts, deposits or other obligations of any bank or savings association and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

This document is dated [—], and is first being mailed to shareholders of North Valley and TriCo on or about [—].

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WHERE YOU CAN FIND MORE INFORMATION

Both TriCo and North Valley file annual, quarterly and special reports, proxy statements and other business and financial information with the Securities and Exchange Commission, which we refer to as the SEC. You may read and copy any materials that either TriCo or North Valley files with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Room 1580, Washington, D.C. 20549, at prescribed rates. Please call the SEC at (800) SEC-0330 ((800) 732-0330) for further information on the public reference room. In addition, TriCo and North Valley file reports and other business and financial information with the SEC electronically, and the SEC maintains a website located at http://www.sec.gov containing this information. You will also be able to obtain these documents, free of charge, from TriCo at www.tcbk.com/about/investor-relations/sec-filings/ or from North Valley by accessing North Valley’s website at http://www.novb.com/shareholderrelations.aspx.

TriCo has filed a registration statement on Form S-4 of which this document forms a part. As permitted by SEC rules, this document does not contain all of the information included in the registration statement or in the exhibits or schedules to the registration statement. You may read and copy the registration statement, including any amendments, schedules and exhibits at the addresses set forth below. Statements contained in this document as to the contents of any contract or other documents referred to in this document are not necessarily complete. In each case, you should refer to the copy of the applicable contract or other document filed as an exhibit to the registration statement. This document incorporates by reference documents that TriCo and North Valley have previously filed with the SEC. They contain important information about the companies and their financial condition. For further information, please see the section entitled “Incorporation of Certain Documents by Reference” beginning on page 156. These documents are available without charge to you upon written or oral request to the applicable company’s principal executive offices. The respective addresses and telephone numbers of such principal executive offices are listed below.

To obtain timely delivery of these documents, you must request the information no later than[—] in order to receive them before TriCo’s annual meeting of shareholders and no later than[—] in order to receive them before North Valley’s special meeting of shareholders.

TriCo common stock is traded on the NASDAQ Global Select Market under the symbol “TCBK,” and North Valley common stock is traded on the NASDAQ Global Select Market under the symbol “NOVB.”

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TRICO BANCSHARES

63 CONSTITUTION DRIVE

CHICO, CALIFORNIA 95973

NOTICE OF THE ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD ON [—], 2014

NOTICE IS HEREBY GIVEN that the annual meeting(Exact name of the shareholders of TriCo Bancshares, which we refer toRegistrant as TriCo, will be held at 63 Constitution Drive, Chico, California at [—], Pacific time, on [—], 2014, for the following purposes:

1. To approve the merger and to approve and adopt the Agreement and Plan of Merger and Reorganization, which we refer to as the merger agreement, dated as of January 21, 2014, by and between TriCo and North Valley, as such agreement may be amended from time to time, a copy of which is attached as Appendix A to this document, and to approve the issuance of TriCo common stock to North Valley shareholders pursuant to the merger agreement, which we refer to as the TriCo Merger proposal;

2. To elect nine directors for terms expiring at the 2015 annual meeting of shareholders;

3. To reapprove the existing performance criteria under the TriCo 2009 equity incentive plan;

4. To approve an advisory resolution concerning the compensation of TriCo executives;

5. To ratify the selection of Crowe Horwath LLP as TriCo’s principal independent auditor for 2014;

6. To approve one or more adjournments of the TriCo annual meeting, if necessary or appropriate, including adjournments to permit further solicitation of proxies in favor of the above referenced proposals, which we refer to as the TriCo Adjournment proposal;

7. To attend to any other business properly presented at the meeting.

TriCo will transact no other business at the annual meeting, except for business properly brought before the annual meeting or any adjournment thereof.

The TriCo Merger proposal is described in more detail in this document, which you should read carefullyspecified in its entirety before you vote. A copy of TriCo’s Annual Report on Form 10-K is enclosed. TriCo is mailing these proxy materials to its shareholders beginning on or about [—].

The TriCo board of directors has set [—] as the record date for the TriCo annual meeting. Only holders of record of TriCo common stock at the close of business on [—] will be entitled to notice of and to vote at the TriCo annual meeting and any adjournment thereof. Any shareholder entitled to attend and vote at the TriCo annual meeting is entitled to appoint a proxy to attend and vote on such shareholder’s behalf. Such proxy need not be a holder of TriCo common stock.

Your vote is very important. To ensure your representation at the TriCo annual meeting, please complete and return the enclosed proxy card or submit your proxy by telephone or through the Internet. Whether or not you expect to attend the TriCo annual meeting, please vote promptly. Submitting a proxy now will not prevent you from being able to vote in person at the TriCo annual meeting.charter)

Chico, California

[—], 2014

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QUESTIONS AND ANSWERS ABOUT THE SHAREHOLDERS’ MEETINGS

The following are answers to certain questions that you may have regarding the shareholders’ meetings. We urge you to read carefully the remainder of this document because the information in this section may not provide all the information that might be important to you in determining how to vote. Additional important information is also contained in the appendices to, and the documents incorporated by reference in, this document.

The merger cannot be completed unless TriCo shareholders approve the merger and approve and adopt the merger agreement and approve the issuance of TriCo common stock in the merger and North Valley shareholders approve the merger and approve and adopt the merger agreement. At each of the shareholders’ meetings, TriCo and North Valley shareholders will vote on the proposals necessary to complete the merger. Information about these shareholders’ meetings, the merger and the other business to be considered by shareholders at each of the shareholders’ meetings is contained in this document.

This document constitutes both a joint proxy statement of TriCo and North Valley and a prospectus of TriCo. It is a joint proxy statement because each of the boards of directors of TriCo and North Valley is soliciting proxies using this document from their respective shareholders. It is a prospectus because TriCo, in connection with the merger, is offering shares of its common stock in exchange for outstanding shares of North Valley common stock in the merger.

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North Valley Special Meeting. Holders of record of North Valley common stock at the close of business on [—], which is the date that the North Valley board of directors has fixed as the record date for the North Valley special meeting, are entitled to vote at the North Valley special meeting.

North Valley Special Meeting. The presence at the North Valley special meeting, in person or by proxy, of holders of a majority of the outstanding shares of North Valley common stock entitled to vote at the North Valley special meeting will constitute a quorum for the transaction of business. Abstentions and broker non-votes, if any, will be included in determining the number of shares present at the meeting for the purpose of determining the presence of a quorum.

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Shareholder approval of the TriCo Merger proposal is required to complete the merger. TriCo will transact no other business at the TriCo annual meeting, except for business properly brought before the TriCo annual meeting or any adjournment or postponement thereof.

North Valley shareholders are being asked to vote on the following proposals:

Shareholder approval of the North Valley Merger proposal is required for completion of the merger. North Valley will transact no other business at the North Valley special meeting, except for business properly brought before the North Valley special meeting or any adjournment or postponement thereof.

Election of Directors: The nine nominees for director who receive the most votes will be elected.

2009 equity incentive plan proposal: Assuming a quorum is present, the affirmative vote of a majority of the shares of TriCo common stock represented (in person or by proxy) at the TriCo annual meeting and entitled to vote on the proposal is required to reapprove the existing performance criteria under the TriCo 2009 equity incentive plan.

Advisory vote on executive compensation proposal: Assuming a quorum is present, the affirmative vote of a majority of the shares of TriCo common stock represented (in person or by proxy) at the TriCo annual meeting and entitled to vote on the proposal is required to approve the advisory vote on executive compensation proposal.

Ratification of principal independent auditor proposal: Assuming a quorum is present, the affirmative vote of a majority of the shares of TriCo common stock represented (in person or by proxy) at the TriCo annual meeting and entitled to vote on the proposal is required to approve the principal independent auditor proposal.

TriCo Adjournment proposal: Assuming a quorum is present, the affirmative vote of a majority of the shares of TriCo common stock represented (in person or by proxy) at the TriCo annual meeting and entitled to vote on the proposal is required to approve the TriCo Adjournment proposal.

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North Valley Advisory (Non-Binding) Proposal on Specified Compensation: Assuming a quorum is present, the affirmative vote of a majority of the shares of North Valley common stock represented (in person or by proxy) at the North Valley special meeting and entitled to vote on the proposal is required to approve the North Valley Advisory (Non-Binding) Proposal on Specified Compensation.

North Valley Adjournment proposal: Assuming a quorum is present, the affirmative vote of a majority of the shares of North Valley common stock represented (in person or by proxy) at the North Valley special meeting and entitled to vote on the proposal is required to approve the North Valley Adjournment proposal.

You may also cast your vote in person at your respective company’s shareholders’ meeting.

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If your shares are held in “street name,” through a broker, bank or other nominee, that institution will send you separate instructions describing the procedure for voting your shares. “Street name” shareholders who wish to vote at the meeting will need to obtain a proxy form from their broker, bank or other nominee.

North Valley Shareholders. You are entitled to one vote for each share of North Valley common stock that you owned as of the record date. As of the close of business on [—], there were approximately [—] outstanding shares of North Valley common stock. As of that date, approximately [—]% of the outstanding shares of North Valley common stock were beneficially owned by the directors and executive officers of North Valley.

The special meeting of North Valley shareholders will be held at [—] at [—], Pacific time, on [—], 2014. Subject to space availability, all North Valley shareholders as of the North Valley record date, or their duly appointed proxies, may attend the North Valley special meeting. Since seating is limited, admission to the meeting will be on a first-come, first-served basis. Registration and seating will begin at [—], Pacific time.

Under the rules of the NASDAQ, brokers who hold shares in street name for a beneficial owner of those shares typically have the authority to vote in their discretion on “routine” proposals when they have not received instructions from beneficial owners. However, brokers are not allowed to exercise their voting discretion with respect to the approval of matters that the NASDAQ determines to be “non-routine” without specific instructions from the beneficial owner. It is expected that, other than the proposal to ratify TriCo’s independent auditor, all proposals to be voted on at the TriCo annual meeting and the North Valley special meeting are such “non-routine” matters. Broker non-votes occur when a broker or nominee is not instructed by the beneficial owner of shares to vote on a particular proposal for which the broker does not have discretionary voting power.

Assuming a quorum is present, if you are a North Valley shareholder and you do not instruct your broker, bank or other nominee on how to vote your shares:

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Assuming a quorum is present, if you are a TriCo shareholder and you do not instruct your broker, bank or other nominee on how to vote your shares, your broker, bank or other nominee may not vote your shares on the TriCo Merger proposal, which broker non-votes will have the same effect as a vote “AGAINST” such proposal.

If you are a TriCo shareholder and you fail to vote or fail to instruct your broker, bank or other nominee how to vote on the TriCo Merger proposal, it will have the same effect as a vote cast “AGAINST” the TriCo Merger proposal. If you respond with an “abstain” vote on the TriCo Merger proposal, your proxy will have the same effect as a vote cast “AGAINST” the TriCo Merger proposal.

If you are a North Valley shareholder and you fail to vote or fail to instruct your broker, bank or other nominee how to vote on the North Valley Merger proposal, it will have the same effect as a vote cast “AGAINST” the North Valley Merger proposal. If you respond with an “abstain” vote on the North Valley Merger proposal, your proxy will have the same effect as a vote cast“AGAINST” the North Valley Merger proposal.

Abstentions will have no effect on the TriCo proposal for the election of directors.

Abstentions will have no effect on the proposals to reapprove the existing performance criteria under the TriCo 2009 equity incentive plan; the TriCo and North Valley advisory proposals concerning executive compensation, the ratification of TriCo’s principal independent auditor for 2014, and the TriCo Adjournment and the North Valley Adjournment, unless there are insufficient votes in favor of these proposals, such that the affirmative votes constitute less than a majority of the required quorum. In such cases, abstentions will have the same effect as a vote against these proposals.

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If you choose any of these methods, you must take the described action such that the notice, Internet vote or proxy card, as applicable, is received no later than the beginning of the applicable shareholders’ meeting.

You may also change your vote by attending the TriCo or North Valley shareholders’ meeting, as applicable, and voting in person.

If your shares are held in an account at a broker, bank or other nominee, you should contact your broker, bank or other nominee to change your vote.

The merger is intended to qualify, and the obligation of TriCo and North Valley to complete the merger is conditioned upon the receipt of opinions of their respective legal or tax advisors to the effect that the merger will qualify, as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, which we refer to as the Internal Revenue Code. In addition, in connection with the filing of the registration statement of which this document is a part, each of Manatt, Phelps & Phillips, LLP and Crowe Horwath LLP has delivered an opinion to TriCo and North Valley, respectively, to the same effect.

Accordingly, based on the opinions delivered in connection herewith, North Valley shareholders generally will not recognize any gain or loss, except with respect to the cash received instead of a fractional share of TriCo common stock.

For a more detailed discussion of the material United States federal income tax consequences of the transaction, please see the section entitled “Material United States Federal Income Tax Consequences of the Merger” beginning on page 99.

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The consequences of the merger to any particular North Valley shareholder will depend on that shareholder’s particular facts and circumstances. Accordingly, you are urged to consult your tax advisor to determine your tax consequences from the merger.

If you are a North Valley shareholder and have any questions about the proxy materials or if you need assistance submitting your proxy or voting your shares or need additional copies of this document or the enclosed proxy card, you should contact North Valley Investor Relations at (530) 226-2900.

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SUMMARY

This summary highlights selected information included in this document and does not contain all of the information that may be important to you. You should read this entire document and its appendices and the other documents to which we refer before you decide how to vote with respect to each of the proposals. In addition, we incorporate by reference important business and financial information about North Valley and TriCo into this document. For a description of this information, please see the section entitled “Incorporation of Certain Documents by Reference” beginning on page 156. You may obtain the information incorporated by reference into this document without charge by following the instructions in the section entitled “Where You Can Find More Information” in the forepart of this document. Each item in this summary includes a page reference directing you to a more complete description of that item.

Unless the context otherwise requires, throughout this document, “TriCo” refers to TriCo Bancshares, “North Valley” refers to North Valley Bancorp and “we,” “us” and “our” refers collectively to TriCo and North Valley. Also, we refer to the proposed merger of North Valley with and into TriCo Bancshares as the “merger,” the proposed merger of North Valley Bank with and into Tri Counties Bank as the “bank merger” and the Agreement and Plan of Merger and Reorganization, dated as of January 21, 2014, by and between TriCo and North Valley as the “merger agreement.”

The Merger and the Merger Agreement (pages 40 and 80)

The terms and conditions of the merger are contained in the merger agreement, which is attached to this document as Appendix A. We encourage you to read the merger agreement carefully, as it is the legal document that governs the merger.

Under the terms of the merger agreement, North Valley will merge with and into TriCo with TriCo as the surviving corporation. Immediately upon the closing of the merger, North Valley Bank, a wholly owned subsidiary of North Valley, will merge with and into Tri Counties Bank, a wholly owned subsidiary of TriCo, with Tri Counties Bank being the surviving bank.

Merger Consideration (page 40)

In the merger, each share of North Valley common stock, no par value per share, owned by a North Valley shareholder (including the associated preferred stock purchase rights issued pursuant to the Amended and Restated Shareholder Protection Rights Agreement dated as of March 26, 2009, as amended, between North Valley and Computershare, Inc., as Rights Agent) will be converted into the right to receive 0.9433 shares of TriCo common stock, no par value per share. A North Valley shareholder will receive any whole shares of TriCo common stock such holder is entitled to receive and cash in lieu of any fractional shares of TriCo common stock such holder is entitled to receive.

Based on the closing share price of TriCo common stock of $27.93 on January 21, 2014, the last trading day before the announcement of the merger, the value of the merger consideration was $26.35 per share. The value of the TriCo common stock on [—], the most recent day for which information was available prior to the printing and mailing of this document, was [—] based upon the exchange ratio.The share price of TriCo common stock will fluctuate and accordingly, the value of the merger consideration you receive may be different than either of these amounts.

Immediately prior to the effective time of the merger, each outstanding option to purchase shares of North Valley common stock, whether or not then vested and whether or not then exercisable, will be cancelled and the holder of the option will be entitled receive, subject to any required tax withholding, an amount in cash, without interest, from North Valley equal to the excess over the exercise price per share, if any, of 0.9433 multiplied by the weighted average of the closing price for shares of TriCo common stock as quoted on the NASDAQ Global Select Market for the 20 consecutive trading days ending on the trading day immediately prior to the closing date.

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Recommendation of the North Valley Board of Directors (page 29)

After careful consideration, the North Valley board of directors unanimously recommends that North Valley shareholders vote“FOR” the North Valley Merger proposal,“FOR” the North Valley Advisory (Non-Binding) Proposal on Specified Compensation and“FOR” the North Valley Adjournment proposal (if necessary or appropriate).

Each of the directors of North Valley has entered into a shareholder agreement with TriCo and North Valley, pursuant to which they have agreed to vote“FOR” the North Valley Merger proposal and“FOR” the North Valley Adjournment proposal (if necessary or appropriate). For more information regarding the shareholder agreements, please see the section entitled “The Merger Agreement—Shareholder Agreements” beginning on page 96.

For a more complete description of North Valley’s reasons for the merger and the recommendation of the North Valley board of directors, please see the section entitled “Reasons for the Merger and Recommendation of the North Valley Board of Directors” beginning on page 45.

Recommendation of the TriCo Board of Directors (page 35)

After careful consideration, the TriCo board of directors unanimously recommends that TriCo shareholders vote“FOR” the TriCo Merger proposal,“FOR” the election of TriCo’s director nominees,“FOR” the reapproval of the existing performance criteria under the TriCo 2009 equity incentive plan,“FOR” the approval of TriCo’s executive compensation program,“FOR” the ratification of Crowe Horwath LLP as TriCo’s principal independent auditor for 2014, and“FOR” any adjournment of the TriCo annual meeting, if necessary or appropriate, including to permit further solicitation of proxies in favor of the above-listed proposals.

Each of the directors of TriCo has entered into a shareholder agreement with TriCo and North Valley, pursuant to which they have agreed to vote“FOR” the TriCo Merger proposal and “FOR” the TriCo Adjournment proposal (if necessary or appropriate). For more information regarding the shareholder agreements, please see the section entitled “The Merger Agreement—Shareholder Agreements” beginning on page 96.

For a more complete description of TriCo’s reasons for the merger and the recommendations of the TriCo board of directors, please see the section entitled “Recommendation of the TriCo Board of Directors and Reasons for the Merger” beginning on page 59.

Opinion of Financial Advisors (pages 48 and 60)

North Valley Financial Advisor

On January 21, 2014, Sandler O’Neill + Partners, L.P., North Valley’s financial advisor in connection with the merger, rendered an oral opinion to North Valley’s board of directors, which was subsequently confirmed in a written opinion dated the same date that, as of such date and subject to and based on the qualifications and assumptions set forth in its written opinion, the merger consideration (defined as the 0.9433 exchange ratio) in the proposed merger was fair, from a financial point of view, to the common shareholders of North Valley.

The full text of Sandler O’Neill’s opinion, dated January 21, 2014, is attached as Appendix B to this document. You should read the opinion in its entirety for a description of the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by Sandler O’Neill in rendering its opinion.

Sandler O’Neill’s opinion is addressed to North Valley’s board of directors and the opinion is not a recommendation as to how any shareholder of North Valley should vote with respect to the merger or any other matter or as to any action that a shareholder should take with respect to the merger.

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The opinion addresses only the fairness, from a financial point of view, of the merger consideration in the proposed merger to the common shareholders of North Valley, and does not address the underlying business decision of North Valley to engage in the merger, or the relative merits of the merger as compared to any strategic alternatives that may be available to North Valley. Sandler O’Neill will receive a fee for its services, portions of which have been paid, and a significant portion of which will be payable upon consummation of the merger.

For further information, please see the section entitled “The Merger—Opinion of North Valley’s Financial Advisor” beginning on page 48.

TriCo Financial Advisor

Keefe, Bruyette & Woods, Inc., which we refer to as KBW, TriCo’s financial advisor in connection with the merger, provided a fairness opinion to the TriCo board of directors in connection with the merger. At the January 21, 2014 meeting at which TriCo’s board of directors considered and approved the merger agreement, KBW delivered to the board its oral opinion, which was subsequently confirmed in writing, that, as of such date, the exchange ratio was fair to TriCo from a financial point of view.

The full text of KBW’s opinion, dated January 21, 2014, is attached as Appendix C to this document. You should read the opinion in its entirety for a description of the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW in rendering its opinion.

KBW’s opinion is addressed to TriCo’s board of directors and the opinion is not a recommendation as to how any shareholder of TriCo should vote with respect to the merger or any other matter as to any action that a shareholder should take with respect to the merger.

For further information, please see the section entitled “The Merger—Opinion of TriCo’s Financial Advisor” beginning on page 60.

North Valley Special Meeting of Shareholders (page 29)

The North Valley special meeting will be held at [—], Pacific time, on [—], 2014, at [—], located at [—]. At the North Valley special meeting, North Valley shareholders will be asked to approve the North Valley Merger proposal, the North Valley Advisory (Non-Binding) Proposal on Specified Compensation and the North Valley Adjournment proposal.

North Valley’s board of directors has fixed the close of business on [—] as the record date for determining the holders of North Valley common stock entitled to receive notice of and to vote at the North Valley special meeting. Only holders of record of North Valley common stock at the close of business on the North Valley record date will be entitled to notice of and to vote at the North Valley special meeting and any adjournment or postponement thereof. As of the North Valley record date, there were [—] shares of North Valley common stock outstanding and entitled to vote at the North Valley special meeting held by [—] holders of record. Each share of North Valley common stock entitles the holder to one vote on each proposal to be considered at the North Valley special meeting. Each of the directors of North Valley has entered into a shareholder agreement with TriCo and North Valley, pursuant to which they have agreed, solely in their capacity as shareholders of North Valley, to vote all of their shares of North Valley common stock in favor of the North Valley Merger proposal and the North Valley Adjournment proposal to be presented at the special meeting. As of the record date, directors and executive officers of North Valley owned and were entitled to vote [—] shares of North Valley common stock, representing approximately [—]% of the shares of North Valley common stock outstanding on that date. North Valley currently expects that North Valley’s executive officers will vote their shares in favor of the proposals to be presented at the special meeting, although none of them has entered into any agreements obligating them to do so (other than one executive officer who is also a director). As of the record date, TriCo beneficially held [—] shares of North Valley’s common stock.

Approval of the North Valley Merger proposal requires the affirmative vote of a majority of the outstanding shares of North Valley common stock entitled to vote on the proposal. Approval of the North Valley

11

Advisory (Non-Binding) Proposal on Specified Compensation and the North Valley Adjournment proposal each require the affirmative vote of a majority of the shares of North Valley common stock represented (in person or by proxy) at the North Valley special meeting and entitled to vote on the proposal.

TriCo Annual Meeting of Shareholders (page 35)

The TriCo annual meeting will be held at [—], Pacific time, on [—], 2014, at TriCo’s headquarters located at 63 Constitution Drive

Chico, California. At the TriCo annual meeting, TriCo shareholders will be asked to approve the TriCo Merger proposal, the electionCalifornia 95973

(530)898-0300

(Address, including zip code and telephone number, including area code, of TriCo’s directors, the 2009 equity incentive plan proposal, the advisory vote of TriCo’sRegistrant’s principal executive compensation, the ratification of the selection of TriCo’s independent auditor and the TriCo Adjournment proposal.

TriCo’s board of directors has fixed the close of business on [—] as the record date for determining the holders of TriCo common stock entitled to receive notice of and to vote at the TriCo annual meeting. As of the TriCo record date, there were [—] shares of TriCo common stock outstanding and entitled to vote at the TriCo annual meeting held by [—] holders of record. Each share of TriCo common stock entitles the holder to one vote on each proposal to be considered at the TriCo annual meeting. As of the record date, directors and executive officers of TriCo owned and were entitled to vote [—] shares of TriCo common stock, representing approximately [—]% of the shares of TriCo common stock outstanding on that date. Each of the directors of TriCo has entered into a shareholder agreement with TriCo and North Valley, pursuant to which they have agreed, solely in their capacity as shareholders of TriCo, to vote all of their shares of TriCo common stock in favor of the TriCo Merger proposal and the TriCo Adjournment proposal to be presented at the annual meeting. TriCo currently expects that TriCo’s executive officers will vote their shares in favor of the proposals to be presented at the annual meeting, although none of them has entered into any agreements obligating them to do so (other than those executive officers who are also directors).

Approval of the TriCo Merger proposal requires the affirmative vote of a majority of the outstanding shares of TriCo common stock entitled to vote on the proposal. Approval of the other TriCo proposals (other than the election of directors) requires the affirmative vote of a majority of the shares of TriCo common stock represented (in person or by proxy) at the TriCo annual meeting and entitled to vote on the proposal. In the election of directors, the nine nominees who receive the most votes will be elected.

North Valley’s Directors and Executive Officers Have Certain Interests in the Merger (page 72)

Certain of North Valley’s executive officers and directors have financial interests in the merger that are different from, or in addition to, the interests of North Valley’s shareholders. The merger would constitute a “change of control” for purposes of the North Valley Salary Continuation Plan and payments under the Salary Continuation Plan would be due North Valley executive officers at the effective time of the merger. Further, the payment of benefits to executive officers under the North Valley Executed Deferred Compensation Plan would be accelerated upon a “change in control,” if that had been elected by the executive officer, and otherwise would be paid by TriCo following the effective time of the merger in a lump sum or in installments, in each case according to the election made by each executive officer; and the payment of benefits to non-employee directors under the North Valley Director Deferred Fee Plan would be accelerated upon a “change in control” if that had been elected by the director, and otherwise would be paid by TriCo following the effective time of the merger in a lump sum or in installments, in each case according to the election made by each director. In addition, each of North Valley’s executive officers and directors hold equity awards, the treatment of which is described below under “Treatment of North Valley Stock Options”. Under the terms of the merger agreement, three individuals will be designated by the board of directors of TriCo to join the board of directors of TriCo. The designated individuals must be approved by the Nominating and Corporate Governance Committee of the board of directors of TriCo. TriCo and North Valley currently expect to select such individuals shortly prior to the consummation of the transaction. The members of the North Valley board of directors were aware of and considered these interests, among other matters, when they approved the merger agreement and unanimously recommended that North Valley shareholders approve the North Valley Merger proposal. These interests are described in more detail under the section entitled “The Merger—Interests of North Valley Directors and Executive Officers in the Merger” beginning on page 72.

Treatment of North Valley Stock Options (page 41)

Immediately prior to the effective time of the merger, each outstanding option to purchase shares of North Valley common stock, whether or not then vested and whether or not then exercisable, will be cancelled and the holder of the option will be entitled receive, subject to any required tax withholding, an amount in cash, without interest, from North Valley equal to the excess over the exercise price per share, if any, of 0.9433 multiplied by the weighted average of the closing price for shares of TriCo common stock as quoted on the NASDAQ Global Select Market for the 20 consecutive trading days ending on the trading day immediately prior to the closing date.

12

Regulatory Approvals Required for the Merger (page 77)

Completion of the merger and the bank merger are subject to various regulatory approvals, including approvals from the California Department of Business Oversight, which we refer to as the Department of Business Oversight, the Federal Deposit Insurance Corporation, which we refer to as the FDIC, and the Board of Governors of the Federal Reserve System, which we refer to as Federal Reserve Board. Notifications and/or applications requesting approval for the merger or for the bank merger may also be submitted to other federal and state regulatory authorities and self-regulatory organizations. We have filed, or are in the process of filing all notices and applications to obtain the necessary regulatory approvals. Although we currently believe we should be able to obtain all required regulatory approvals, we cannot be certain when or if we will obtain them or, if obtained, whether they will contain terms, conditions or restrictions not currently contemplated that will be detrimental to or have a material adverse effect on the combined company after the completion of the merger. The regulatory approvals to which completion of the merger and bank merger are subject are described in more detail under the section entitled “The Merger—Regulatory Approvals Required for the Merger” beginning on page 77.

Conditions to the Merger (page 93)

The obligations of TriCo and North Valley to complete the merger are each subject to the satisfaction or waiver of the following conditions:

Richard P. Smith

President and approval of the North Valley Merger proposal by the North Valley shareholders;

Chief Executive Officer

13

No Solicitation (page 88)

Under the terms of the merger agreement, North Valley has agreed not to solicit, initiate or knowingly encourage inquiries or proposals with respect to, or engage or participate in any discussions or negotiations concerning, or provide any confidential or nonpublic information or data to, any person relating to, any acquisition proposal. Notwithstanding these restrictions, the merger agreement provides that, under specified circumstances, in response to an unsolicited bona fide acquisition proposal which, in the good faith judgment of the North Valley board of directors, is or is reasonably likely to result in a proposal which is superior to the merger with TriCo, and the North Valley board of directors determines in good faith (and after consultation with North Valley’s outside counsel) that failure to take such actions would reasonably be expected to be a violation of its fiduciary duties under applicable law, North Valley may furnish information regarding North Valley and participate in discussions and negotiations with such third party.

Termination; Termination Fee (page 94)

TriCo and North Valley may mutually agree at any time to terminate the merger agreement without completing the merger, even if the North Valley shareholders have approved the merger and approved and adopted the merger agreement and the TriCo shareholders have approved the merger and approved and adopted the merger agreement and approved the issuance of TriCo common stock in connection with the merger.

The merger agreement may also be terminated and the merger abandoned at any time prior to the effective time of the merger, as follows:

14

North Valley may be required to pay TriCo a termination fee of $7.6 million in certain circumstances. TriCo may be required to pay North Valley a termination fee of $3.8 million in certain other circumstances. For more information, please see the section entitled “The Merger Agreement—Termination; Termination Fee” beginning on page 94.

Material United States Federal Income Tax Consequences of the Merger (page 15)

The merger is intended to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code. Assuming the merger qualifies as such a reorganization, a shareholder of North Valley generally will not recognize any gain or loss upon receipt of TriCo common stock in exchange for North Valley common stock in the merger, except with respect to cash received in lieu of a fractional share of TriCo common stock. It is a condition to the completion of the merger that TriCo and North Valley receive written opinions from their legal or tax advisors to the effect that the merger will qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code.

Tax matters are very complicated and the tax consequences of the merger to each North Valley shareholder may depend on such shareholder’s particular facts and circumstances. North Valley shareholders are urged to consult their tax advisors to understand fully the tax consequences to them of the merger. For more information, please see the section entitled “Material United States Federal Income Tax Consequences of the Merger” beginning on page 15.

Litigation Related to the Merger (page 99)

On January 24, 2014, a purported shareholder of North Valley filed a lawsuit in connection with the merger. CaptionedSolak v. North Valley Bancorp, et al., Case No. 179099, the suit was filed in the Superior Court of the State of California, Shasta County, against North Valley, its directors, and TriCo. For more information, please see the section entitled “Litigation Related to the Merger” beginning on page 99.

Comparison of Shareholders’ Rights (page 107)

The rights of North Valley shareholders who continue as TriCo shareholders after the merger will be governed by the articles of incorporation and bylaws of TriCo rather than by the articles of incorporation and bylaws of North Valley. For more information, please see the section entitled “Comparison of Shareholders’ Rights” beginning on page 107.

Information About the Companies (page 28)

TriCo Bancshares

63 Constitution Drive

Chico, California 95973

(530)898-0300

(Name, address, including zip code, and telephone number, including area code, of agent for service)

with a copy to:

Approximate date of commencement of proposed sale to the public:

As soon as practicable following the effectiveness of this Registration Statement, satisfaction or waiver of the other conditions to closing of the merger described herein, and consummation of the merger.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box.  ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, anon-accelerated filer or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer,” and “smaller reporting company” in Rule12b-2 of the Exchange Act. (Check one):

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule13e-4(i) (Cross-Border Issuer Tender Offer)  ☐

Exchange Act Rule14d-1(d) (Cross-Border Third-Party Tender Offer)  ☐

Calculation of Registration Fee

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

Information contained herein is subject to completion or amendment. A registration statement relating to these securities has been filed with the Securities and Exchange Commission. These securities may not be sold prior to the time the registration statement becomes effective. This document shall not constitute an offer to sell nor shall there be any sale of these securities in any jurisdiction in which such offer or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

PRELIMINARY—SUBJECT TO COMPLETION—DATED MARCH 21, 2018

The information in this joint proxy statement/prospectus is not complete and may be changed. We may not offer or sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This joint proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED MARCH 21, 2018

63 Constitution Drive

Chico, California 95973

Dear TriCo Bancshares is a bank holding company registered under the Bank Holding Company ActShareholders:

On December 11, 2017, TriCo Bancshares, which we refer to as TriCo, entered into an agreement and plan of 1956, as amended,merger and reorganization, which we refer to as the BHC Act. merger agreement, to acquire FNB Bancorp, which we refer to as FNBB. If the required shareholder and regulatory approvals are obtained and all closing conditions are satisfied or waived, FNBB will merge with and into TriCo, with TriCo as the surviving corporation, which we refer to as the merger. Immediately after the merger, FNBB’s wholly-owned bank subsidiary, First National Bank of Northern California, will merge with and into Tri Counties Bank, the wholly-owned bank subsidiary of TriCo, with Tri Counties Bank as the surviving bank.

You are cordially invited to attend a special meeting of shareholders of TriCo to be held at [●], Pacific Time, on [●], 2018 at 890 Fortress Street, Chico, California 95973. At the special meeting, TriCo shareholders will be asked to consider and vote upon a proposal to approve the merger agreement, including the merger and the issuance of shares of TriCo common stock in connection with the merger, which we refer to as the merger proposal. FNBB will also hold a special meeting of shareholders to consider the proposed merger agreement and related matters. TriCo and FNBB cannot complete the proposed merger unless TriCo’s shareholders vote to approve the merger proposal. This letter is accompanied by the attached joint proxy statement/prospectus, which TriCo’s board of directors is providing to solicit your proxy to vote for the approval of the merger proposal.

If the merger is completed, each outstanding share of FNBB common stock will be canceled and converted into the right to receive 0.98 shares of TriCo common stock, which we refer to as the exchange ratio. Cash will be paid in lieu of any fractional shares.

As described in the attached joint proxy statement/prospectus, the exchange ratio is subject to potential adjustment. The exchange ratio could change depending on the weighted average closing price of TriCo common stock reported on the Nasdaq Global Select Market over the 20 trading days ending five business days prior to the completion of the merger, which we refer to as the TriCo average closing price.

On [●], 2018, the actual closing price for TriCo common stock reported on the Nasdaq Global Select Market was $[●] per share. If the merger had been completed on that date, the TriCo average closing price would have been $[●] and the exchange ratio would have remained unchanged at 0.98 shares of TriCo common stock. The actual exchange ratio will not be known until the merger is completed.

Based on the closing price of TriCo common stock as reported on the Nasdaq Global Select Market of $41.64 as of December 31, 2013, TriCo had consolidated total assets8, 2017, the trading day immediately preceding the public announcement of the merger, the implied merger consideration that an FNBB shareholder would be entitled to receive for each share of FNBB common stock owned would be $40.81 with an aggregate transaction value of approximately $2.7 billion, total gross loans$315 million. Based on the closing price of TriCo common stock as reported on the Nasdaq Global Select Market of $[●] as of [●], 2018, the latest practicable date before the date of this joint proxy statement/prospectus, the implied merger consideration that an FNBB shareholder would be entitled to receive for each share of FNBB common stock owned would be $[●] with an aggregate transaction value of approximately $1.7 billion,$[● ] million. The value of the merger consideration will fluctuate based on the market price of TriCo common stock.

Consequently, the value of the merger consideration will not be known at the time you vote on the merger proposal. Based on the current number of shares of FNBB common stock outstanding, TriCo expects to issue approximately [●] shares of common stock in the aggregate upon completion of the merger and FNBB’s current shareholders would own approximately 24% of the combined company.TriCo’s common stock is listed on the Nasdaq Global Select Market under the symbol “TCBK.”FNBB’s common stock is listed on the Nasdaq Global Select Market under the symbol “FNBG.” You should obtain current market quotations for TriCo common stock and FNBB common stock before you vote on the merger proposal.

Based on our reasons for the merger described in the accompanying document, including the fairness opinion issued by our financial advisor, Stephens Inc., our board of directors believes that the merger is fair to and in the best interests of TriCo shareholders.Accordingly, the TriCo board of directors unanimously recommends that you vote “FOR” the merger proposal. The accompanying joint proxy statement/prospectus gives you detailed information about the special meeting, the merger and the issuance of shares of TriCo common stock in connection with the merger and related matters. In addition to being a proxy statement of TriCo for the solicitation of proxies from TriCo shareholders, this document is also the proxy statement for the solicitation of proxies from FNBB shareholders to vote to approve the merger agreement including the merger and is the prospectus of TriCo for the shares of its common stock that will be issued to FNBB shareholders in connection with the merger.

We advise you to read this entire document carefully, including the considerations discussed under “Risk Factors” beginning on page 29, and the appendices to the accompanying joint proxy statement/prospectus, which include the merger agreement.

Your vote is very important. The merger cannot be completed unless the holders of a majority of the outstanding shares vote in favor of approval of the merger proposal. Whether or not you plan to attend the special meeting, please take the time to vote by completing and mailing the enclosed proxy card or by following the instructions to vote via the Internet or by telephone indicated on the proxy card.

We appreciate your continuing loyalty and support and, should you choose to attend, we look forward to seeing you at the special meeting.

Sincerely,

Richard P. Smith

President and Chief Executive Officer

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the shares of TriCo common stock to be issued in the merger or determined if this joint proxy statement/prospectus is accurate or adequate. Any representation to the contrary is a criminal offense.

The securities to be issued in connection with the merger are not savings accounts, deposits or other obligations of approximately $2.4 billionany bank or savings association and shareholders’ equityare not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

This joint proxy statement/prospectus is dated [●], 2018 and is being first mailed to shareholders of approximately $250.9 million. TriCo had 733 full-time equivalent employees of December 31, 2013.and FNBB on or about [●], 2018.

The information in this joint proxy statement/prospectus is not complete and may be changed. We may not offer or sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This joint proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

15SUBJECT TO COMPLETION, DATED MARCH 21, 2018

975 El Camino Real

South San Francisco, California 94080

Dear FNB Bancorp Shareholders:

On December 11, 2017, TriCo Bancshares, which we refer to as TriCo, entered into an agreement and plan of merger and reorganization, which we refer to as the merger agreement, to acquire FNB Bancorp, which we refer to as FNBB. If the required shareholder and regulatory approvals are obtained and all closing conditions are satisfied or waived, FNBB will be merged with and into TriCo, with TriCo as the surviving corporation, which we refer to as the merger. Immediately after the merger, FNBB’s wholly-owned bank subsidiary, First National Bank of Northern California, will merge with and into Tri Counties Bank, the wholly-owned bank subsidiary of TriCo, with Tri Counties Bank as the surviving bank.

You are cordially invited to attend a special meeting of shareholders of FNBB to be held at [●], Pacific Time, on [●], 2018 at The Basque Cultural Center, 599 Railroad Avenue, South San Francisco, California 94080. At the special meeting, the FNBB shareholders will be asked to consider and vote upon a proposal to approve the merger agreement and the merger. You will also be asked to approve, on an advisory(non-binding) basis, the compensation that may be payable to FNBB’s named executive officers in connection with the merger, and to approve adjournments of the special meeting, if necessary, to permit further solicitation of proxies in favor of the foregoing proposals. TriCo will also hold a special meeting of shareholders to approve the merger agreement and the issuance of shares of TriCo common stock in connection with the merger. TriCo and FNBB cannot complete the proposed merger unless FNBB’s shareholders vote to approve the merger agreement and the merger. This letter is accompanied by the attached joint proxy statement/prospectus, which FNBB’s board of directors is providing to solicit your proxy to vote for the approval of the merger agreement and the merger.

If the merger is completed, each outstanding share of FNBB common stock will be cancelled and converted into the right to receive 0.98 shares of TriCo common stock, which we refer to as the exchange ratio. Cash will be paid in lieu of any fractional shares.

As described in the attached joint proxy statement/prospectus, the exchange ratio is subject to potential adjustment. The exchange ratio could change depending on the weighted average closing price of TriCo common stock reported on the Nasdaq Global Select Market over the 20 trading days ending five business days prior to the completion of the merger, which we refer to as the TriCo average closing price.

North Valley BancorpOn [●], 2018, the actual closing price for TriCo common stock reported on the Nasdaq Global Select Market was $[●] per share. If the merger had been completed on that date, the TriCo average closing price would have been $[●] and the exchange ratio would have remained unchanged at 0.98 shares of TriCo common stock. The actual exchange ratio will not be known until the merger is completed.

300 Park Marina Circle

Redding, California 96001

(530) 226-2900

North Valley Bancorp is a bank holding company registered underBased on the BHC Act. Asclosing price of December 31, 2013, North Valley had consolidated total assetsTriCo common stock as reported on the Nasdaq Global Select Market of approximately $917.8 million, total gross loans of approximately $509.2 million, deposits of approximately $787.8 million and shareholders’ equity of approximately $93.4 million. North Valley had 297 full-time equivalent employees$41.64 as of December 31, 2013.8, 2017, the trading day immediately preceding the public announcement of the merger, the implied merger consideration that an FNBB shareholder would be entitled to receive for each share of FNBB common stock owned would be $40.81 with an aggregate transaction value of approximately $315 million. Based on the closing price of TriCo common stock as reported on the Nasdaq Global Select Market of $[●] as of [●], 2018, the latest practicable date before the date of this joint proxy statement/prospectus, the implied merger consideration that an FNBB shareholder would be entitled to receive for each share of FNBB common stock owned would be $[●] with an aggregate transaction value of approximately $[●] million. The value of the merger consideration will fluctuate based on the market price of TriCo common stock. Based on the number of shares of TriCo common stock outstanding as of the date of this document, TriCo expects to issue approximately [●] shares of common stock in the aggregate upon completion of the merger.TriCo’s common stock is listed on the Nasdaq Global Select Market under the symbol “TCBK”. FNBB’s common stock is listed on the Nasdaq Global Select Market under the symbol “FNBG.” You should obtain current market quotations for TriCo common stock and FNBB common stock before you vote on the merger proposal.

Based on our reasons for the merger described in the accompanying document, including the fairness opinion issued by our financial advisor, The Courtney Group, LLC, the FNBB board of directors believes that the exchange ratio is fair to and in the best interests of FNBB shareholders.

Accordingly, FNBB’s board of directors unanimously recommends that you vote “FOR” the merger agreement and the merger, “FOR” the proposal to approve, on an advisory(non-binding) basis, the compensation that may be payable to FNBB’s named executive officers in connection with the merger, and “FOR” the proposal to approve adjournments of the special meeting, if necessary. The accompanying joint proxy statement/prospectus gives you detailed information about the special meeting, the merger and related matters. In addition to being a proxy statement of FNBB, this document is the proxy statement for the solicitation of proxies from TriCo shareholders to vote to approve the merger agreement and the transactions contemplated therein, including the merger, and the issuance of shares of TriCo common stock in connection with the merger and is the prospectus of TriCo for the shares of TriCo common stock that will be issued to the FNBB shareholders in connection with the merger.

We advise you to read this entire document carefully, including the considerations discussed under “Risk Factors (page 23)” beginning on page 29, and the appendices to the accompanying joint proxy statement/prospectus, which include the merger agreement.

Before votingYour vote is very important. The merger cannot be completed unless the holders of a majority of the outstanding shares of FNBB common stock vote in favor of approval of the merger agreement and the transactions contemplated therein, including the merger, at the special meeting. Whether or not you plan to attend the special meeting, please take the time to vote by completing and mailing the enclosed proxy card or by following the instructions to vote via the Internet or by telephone indicated on the proxy card.

We appreciate your continuing loyalty and support and, should you choose to attend, we look forward to seeing you at the special meeting.

Sincerely,

Thomas C. McGraw

Chief Executive Officer

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the shares of TriCo common stock to be issued in connection with the merger or determined if this joint proxy statement/prospectus is accurate or adequate. Any representation to the contrary is a criminal offense.

The securities to be issued in connection with the merger are not savings accounts, deposits or other obligations of any bank or savings association and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

This joint proxy statement/prospectus is dated [●], 2018 and is being first mailed to shareholders of FNBB and TriCo on or about [●], 2018.

TRICO BANCSHARES

63 Constitution Drive

Chico, California 95973

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

To be held on [●], 2018

To the shareholders of TriCo Bancshares:

We will hold a special meeting of shareholders of TriCo Bancshares, or TriCo, at [●], Pacific Time, on [●], 2018 at 890 Fortress Street, Chico, California 95973, for the following purposes:

1.Approval of Merger Agreement. To consider and vote upon a proposal to approve the agreement and plan of merger and reorganization, dated as of December 11, 2017, by and between TriCo and FNB Bancorp, referred to in this notice as the merger agreement, pursuant to which (i) FNB Bancorp will merge with and into TriCo, with TriCo as the surviving corporation, which we refer to in this notice as the merger, and (ii) TriCo will issue shares of TriCo common stock in exchange for outstanding shares of FNB Bancorp common stock in accordance with the merger agreement, all of which we refer to as the merger proposal. A copy of the merger agreement is attached as Appendix A to the accompanying joint proxy statement/prospectus of which this notice is a part.

2.Adjournment. To consider and vote upon a proposal to adjourn the special meeting to a later date or dates, if necessary, to permit further solicitation of proxies if there are not sufficient votes at the time of the TriCo special meeting to approve the merger proposal.

No other business may be conducted at the special meeting.

We have fixed the close of business on [●], 2018 as the record date for the determination of shareholders entitled to notice of and to vote at the special meeting. Only holders of TriCo common stock of record at the close of business on that date will be entitled to notice of and to vote at the special meeting or any adjournment or postponement of the special meeting.

The TriCo board of directors has unanimously approved the merger agreement and the transactions contemplated therein and has determined that the merger is in the best interests of TriCo and its shareholders, and unanimously recommends that shareholders vote “FOR” approval of the merger proposal and “FOR” approval of the proposal to adjourn the TriCo special meeting to a later date or dates, if necessary, to permit further solicitation of proxies if there are not sufficient votes at the time of the special meeting to approve the merger proposal.

If you have any questions concerning the merger or the joint proxy statement/prospectus, please contact Richard P. Smith, TriCo’s President and Chief Executive Officer, at (530) 898-0300. If you would like additional copies of the joint proxy statement/prospectus or if you need help voting your shares of TriCo common stock, please contact Craig Compton, TriCo’s Corporate Secretary, at (530)898-0300.

Your vote is very important. Whether or not you plan to attend the TriCo special meeting, please promptly complete, sign, date and return your proxy card in the enclosed envelope or vote via the Internet or by telephone pursuant to the instructions provided on the enclosed proxy card.

By Order of the Board of Directors

Craig S. Compton

Secretary

Chico, California

[●], 2018

FNB Bancorp

975 El Camino Real

South San Francisco, California 94080

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

To be held on [●], 2018

To the shareholders of FNB Bancorp:

We will hold a special meeting of shareholders of FNB Bancorp, or FNBB, at [●] p.m., Pacific Time, on [●], 2018 at The Basque Cultural Center, 599 Railroad Avenue, South San Francisco, California 94080 for the following purposes:

1.Approval of the Merger Agreement. To consider and vote upon a proposal to approve an agreement and plan of merger and reorganization, dated as of December 11, 2017, by and between TriCo Bancshares, or TriCo, and FNBB, which we refer to in this notice as the merger agreement, pursuant to which FNBB will merge with and into TriCo with TriCo as the surviving corporation, which we refer to as the merger. A copy of the merger agreement is attached as Appendix A to the accompanying joint proxy statement/prospectus of which this notice is a part;

2.Advisory(Non-Binding) Vote on Certain Compensatory Arrangements. To consider and vote on a proposal to approve, on an advisory(non-binding) basis, the compensation that may be payable to FNBB’s named executive officers in connection with the merger, and the agreements and understandings pursuant to which such compensation may be paid or become payable, as described in the section entitled “The Merger—Interests of Certain FNBB Officers and Directors in the Merger—Merger-Related Compensatory Arrangements for FNBB’s Named Executive Officers” beginning on page [●]; and

3.Adjournment. To consider and vote upon a proposal to adjourn the special meeting to a later date or dates, if necessary, to permit further solicitation of proxies if there are not sufficient votes at the time of the special meeting to approve the merger agreement.

No other business may be conducted at the special meeting.

We have fixed the close of business on [●], 2018 as the record date for the determination of shareholders entitled to notice of and to vote at the FNBB special meeting. Only holders of FNBB common stock of record at the close of business on that date will be entitled to notice of and to vote at the FNBB special meeting or any adjournment or postponement of the special meeting.

The FNBB board of directors has unanimously approved the merger agreement and the transactions contemplated therein. Based on FNBB’s reasons for the merger described in the attached joint proxy statement/prospectus, the FNBB board of directors has determined that the merger is in the best interests of FNBB and its shareholders, and unanimously recommends that shareholders vote “FOR” approval of the merger proposal “FOR” the proposal to approve, on an advisory(non-binding) basis, the compensation that may be payable to FNBB’s named executive officers in connection with the merger, and “FOR” approval of the proposal to adjourn the FNBB special meeting to a later date or dates, if necessary, to permit further solicitation of proxies if there are not sufficient votes at the time of the FNBB special meeting to approve the merger proposal.

If you have any questions concerning the merger or the joint proxy statement/prospectus, if you would like additional copies of the joint proxy statement/prospectus or if need help voting your shares of FNBB common stock, please contact Thomas C. McGraw, FNBB’s Chief Executive Officer, at (650)588-6800.

Your vote is very important. Whether or not you plan to attend the special meeting, please promptly complete, sign, date and return your proxy card in the enclosed envelope or vote via the Internet or by telephone pursuant to the instructions provided on the enclosed proxy card.

By Order of the Board of Directors

Edward J. Watson

Secretary

South San Francisco, California

[●], 2018

TABLE OF CONTENTS

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WHERE YOU CAN FIND MORE INFORMATION

Both TriCo Bancshares, which we refer to as TriCo, and FNB Bancorp, which we refer to as FNBB, file annual, quarterly and current reports, proxy statements and other business and financial information with the Securities and Exchange Commission, which we refer to as the SEC. You may read and copy any materials that either TriCo or North Valley shareholders’ meeting, you should carefully considerFNBB files with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Room 1580, Washington, D.C. 20549, at prescribed rates. Please call the SEC at(800) SEC-0330 ((800)732-0330) for further information on the public reference room. In addition, TriCo and FNBB file reports and other business and financial information with the SEC electronically, and the SEC maintains a website located at http://www.sec.gov containing this information. You can also obtain, free of charge, documents that TriCo files with the SEC at www.tcbk.com under the tab “About Us” and then under the heading “Investor Relations” or documents that FNBB files with the SEC at www.fnbnorcal.com under the link “Investor Relations.” The information provided on (or accessible through) the TriCo and FNBB websites is not part of this joint proxy statement/prospectus and is not incorporated herein by reference unless specifically stated. Copies of the documents that TriCo or FNBB, respectively, files with the SEC can also be obtained, free of charge, by directing a request to TriCo or FNBB at the following respective addresses and phone numbers:

TriCo has filed a registration statement on FormS-4 to register with the SEC the shares of TriCo common stock as specified therein. This joint proxy statement/prospectus is a part of that registration statement. As permitted by SEC rules, this document does not contain all of the information included in the registration statement or in the exhibits or schedules to the registration statement. You may read and copy the registration statement, including any amendments, schedules and exhibits, at the addresses set forth above. Statements contained in this document as to the contents of any contract or incorporated by reference intoother documents referred to in this document are not necessarily complete. In each case, you should refer to the copy of the applicable contract or other document filed as an exhibit to the registration statement of which this joint proxy statement/prospectus is a part. This document incorporates important business and financial information about TriCo that is not included in or delivered with this document, including the risk factors set forth in the section entitled “Risk Factors” beginning on page 23 or described in TriCo’s and North Valley’s Annual Reports on Form 10-K for the year ended on December 31, 2013 and other reportsincorporating by reference documents that TriCo has previously filed with the SEC,SEC. See “Documents Incorporated by Reference.” These documents are available without charge to you upon written or oral request to TriCo’s principal executive offices listed above.

If any TriCo shareholder or FNBB shareholder would like to request documents, please do so by [●], 2018, which is five business days prior to the date of the special meetings, in order to provide sufficient time receive them before the special meeting of TriCo shareholders, which we refer to as the TriCo special meeting, or the special meeting of FNBB shareholders, which we refer to as the FNBB special meeting, as the case may be. You will not be charged for any of these documents.

QUESTIONS AND ANSWERS

ABOUT THE MERGER AND THE SPECIAL MEETINGS

The following are some questions that you may have regarding the merger and the special meetings, and brief answers to those questions. TriCo and FNBB advise you to read carefully the remainder of this joint proxy statement/prospectus because the information in this section does not provide all of the information that might be important to you with respect to the merger and the special meetings of TriCo and FNBB. Additional important information is also contained in the documents incorporated by reference into this joint proxy statement/prospectus. Please seeSee “Where You Can Find More Information” beginning on page v.

Q: What am I being asked to vote on?

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SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA FOR TRICOA:

The following table summarizes consolidated financial results achieved by TriCo forand FNBB have entered into an agreement and plan of merger and reorganization, which we refer to as the periodsmerger agreement, pursuant to which TriCo has agreed to acquire FNBB. If the required shareholder and at the dates indicated and should be read in conjunction with TriCo’s consolidated financial statementsregulatory approvals are obtained and the notesmerger is subsequently completed, FNBB will be merged with and into TriCo with TriCo continuing as the surviving corporation. Immediately thereafter, FNBB’s wholly-owned bank subsidiary, First National Bank of Northern California, which we refer to as First National Bank, will merge with and into Tri Counties Bank, the consolidated financial statements contained in reports that TriCo has previously filed with the SEC. Historical financial information for TriCo can be found in its Annual Report on Form 10-K for the year ended December 31, 2013. Please see the section entitled “Where You Can Find More Information” beginning on page v for instructions on how to obtain the information that has been incorporated by reference. You should not assume the results of operations for past periods indicate results for any future period.

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SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA FOR NORTH VALLEY

The following table summarizes consolidated financial results achieved by North Valley for the periods and at the dates indicated and should be read in conjunction with North Valley’s consolidated financial statements and the notes to the consolidated financial statements contained in reports that North Valley has previously filed with the SEC. Historical financial information for North Valley can be found in its Annual Report on Form 10-K for the year ended December 31, 2013. Please see the section entitled “Where You Can Find More Information” beginning on page v for instructions on how to obtain the information that has been incorporated by reference. You should not assume the results of operations for past periods indicate results for any future period.

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UNAUDITED COMPARATIVE PER COMMON SHARE DATA

The following table shows per common share data regarding basic and diluted earnings, cash dividends, and book value for (a) TriCo and North Valley on a historical basis, (b) TriCo on a pro forma combined basis, and (c) North Valley on a pro forma equivalent basis. The pro forma basic and diluted earnings per share information was computed as if the merger had been completed on January 1, 2013. The pro forma book value per share information was computed as if the merger had been completed on the dates presented.

The following pro forma information has been derived from and should be read in conjunction with TriCo’s and North Valley’s audited consolidated financial statements as of and for the year ended December 31, 2013, incorporated herein by reference. This information is presented for illustrative purposes only. You should not rely on the pro forma combined or pro forma equivalent amounts as they are not necessarily indicative of the operating results or financial position that would have occurred if the merger had been completed as of the dates indicated, nor are they necessarily indicative of the future operating results or financial position of the combined company. The pro forma information, although helpful in illustrating the financial characteristics of the combined company under one set of assumptions, does not reflect the benefits of expected cost savings, opportunities to earn additional revenue, the impact of restructuring and merger-related costs (except merger costs are reflected in the Unaudited Pro Forma Combined Condensed Balance Sheet), or other factors that may result as a consequence of the merger and, accordingly, does not attempt to predict or suggest future results. The information below should be read in conjunction with the section entitled “Unaudited Pro Forma Combined Condensed Financial Statements” beginning on page 101.

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COMPARATIVE PER SHARE MARKET PRICE AND DIVIDEND INFORMATION

The table below sets forth, for the calendar quarters indicated, the high and low sales prices per share, and the dividend paid per share,wholly-owned bank subsidiary of TriCo, common stock, which trades onwith Tri Counties Bank continuing as the NASDAQ Global Select Market under the symbol “TCBK,” and North Valley common stock, which trades on the NASDAQ Global Select Market under the symbol “NOVB.”surviving corporation.

The following table sets forth the closing sale prices per share ofIf you are a TriCo common stock and North Valley common stock on January 21, 2014, the last trading day before the public announcement of the signing ofshareholder, you are being asked to vote to approve the merger agreement and on [—], 2014, the latest practicable date before the date of this document. The following table also includes the equivalent market value per share of North Valley common stock on January 21, 2014 and [—], 2014, determined by multiplying the closing share price of TriCo common stock on such dates by the exchange ratio for the merger of 0.9433.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This document, including information included or incorporated by reference in this document contains forward looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 giving TriCo’s and North Valley’s expectations or predictions of future financial or business performance or conditions. Forward-looking statements are typically identified by words such as “believe,” “expect,” “anticipate,” “intend,” “target,” “estimate,” “continue,” “positions,” “prospects,” “projections” or “potential,” by future conditional verbs such as “will,” “would,” “should,” “could” or “may,” or by variations of such words or by similar expressions. These forward-looking statements are subject to numerous assumptions, risks and uncertainties which change over time. Forward-looking statements speak only as of the date they are made and TriCo and North Valley assume no duty to update forward-looking statements.

In addition to factors previously disclosed in TriCo’s and North Valley’s reports filed with the SEC and those identified elsewhere in this filing (including the section entitled “Risk Factors” beginning on page 23), the following factors among others, could cause actual results to differ materially from forward-looking statements or historical performance:

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RECENT DEVELOPMENTS

TriCo Results for Quarter Ended March 31, 2014 (Unaudited)

On April 29, 2014, TriCo announced its unaudited consolidated financial results for the quarter ended March 31, 2014. TriCo’s net income for the three months ended March 31, 2014 was $7,365,000, or $0.45 per diluted share. These results compare to earnings of $8,477,000, or $0.53 per diluted for the three months ended March 31, 2013.

TriCo’s total assets increased $142,751,000 (5.5%) to $2,755,184,000 at March 31, 2014 from $2,612,433,000 at March 31, 2013. Total investments increased $296,854,000 (192%) to $450,955,000 at March 31, 2014 from $154,101,000 at March 31, 2013. Total loans increased $154,690,000 (10.1%) to $1,687,052,000 at March 31, 2014 from $1,532,362,000 at March 31, 2013. Total deposits increased $125,570,000 (5.5%) to $2,411,120,000 at March 31, 2014 from $2,285,550,000 at March 31, 2013.

Net interest income on a fully-taxable equivalent (“FTE”) basis for the first quarter of 2014 increased $1,524,000 (6.2%) from the same period in 2013 to $26,154,000. The increase in net interest income (FTE) was due primarily to a $242,907,000 (147%) increase in the average balance of investments to $407,848,000, and a $122,666,000 (7.9%) increase in the average balance of loans to $1,671,231,000 that were partially offset by a 54 basis point decrease in the average yield on loans from 6.22% during the three months ended March 31, 2013 to 5.68% during the three months ended March 31, 2014. During much of 2013 and the three months ended March 31, 2014, TriCo used a portion of its Federal funds sold to buy investments. The increase in average loan balances was due to organic loan growth and the purchase of $62,698,000 of loans during 2013. The decrease in average loan yields was due primarily to declines in market yields on new and renewed loans compared to yields on repricing, maturing, and paid off loans. The increases in average investment and loan balances added $1,780,000 and $1,907,000 to net interest income (FTE) while the decrease in average loan yields reduced net interest income (FTE) by $2,241,000 when compared to the year-ago quarter. During much of 2013 and the three months ended March 31, 2014, TriCo deployed some of its excess Federal funds sold into some higher yielding investments while trying to maintain an appropriate level of interest rate risk.

TriCo benefited from a $1,355,000 reversal of provision for loan losses during the three months ended March 31, 2014 versus a benefit of $1,108,000 during the three months ended March 31, 2013. The reversal of provision for loan losses during the first quarter of 2014 was primarily the result of improvements in collateral values and estimated cash flows related to nonperforming originated loans and purchased credit impaired loans, reductions in nonperforming originated loans and purchased credit impaired loans, and decreased loss histories for performing originated loans.

Noninterest income decreased $1,923,000 (18.8%) to $8,295,000 in the three months ended March 31, 2014 compared to the three months ended March 31, 2013. The decrease in noninterest income was due primarily to a $1,830,000 (79.9%) decrease in gain on sale of loans to $464,000, and a $450,000 (14.3%) decrease in service charges on deposit accounts that were partially offset by a $676,000 (123%) increase in gain on sale of foreclosed assets to $1,227,000. The decrease in gain on sale of loans was primarily due to the increase in residential real estate mortgage rates that occurred in 2013 that resulted in a significant decrease in mortgage refinance activity, and thus a significant decrease in newly originated mortgages for TriCo to sell. The decrease in service charges on deposit accounts was primarily due to reduced customer overdrafts and a resulting decrease in non-sufficient funds fees. The increase in gain on sale of foreclosed assets was due to a general increase in property values and sales activity from their lows during the financial crisis that started in 2008.

Salary and benefit expenses increased $342,000 (2.6%) to $13,303,000 during the three months ended March 31, 2014 compared to the three months ended March 31, 2013. Base salaries increased $518,000 (6.2%) to $8,866,000 during the three months ended March 31, 2014 versus the year ago period despite a 1.5% decrease in the average number of full time equivalent employees from 743 to 732. The average number of full time equivalent employees decreased primarily due to the reductions in staff from the closing of five branches since December 31, 2012 that was partially offset by increases in full time equivalent back office staff and management. The salary expense attributable to the newly added back office staff and management outweighed the reduction in salary expense from the branch closings. Annual salary merit increases of approximately 2.5% also contributed to the increase in base salary expense. Incentive and commission related salary expenses decreased $163,000 (12.7%) to $1,123,000 during three months ended March 31, 2014 due primarily to decreases in production related incentives tied to reduced residential real estate mortgage loan originations and sales. Benefits expense, including retirement, medical and workers’ compensation insurance, and taxes, decreased $13,000 (0.4%) to $3,314,000 during the three months ended March 31, 2014.

Other noninterest expenses increased $1,374,000 (15.9%) to $10,014,000 during the three months ended March 31, 2014 compared to the three months ended March 31, 2013. The increase in other noninterest expense was due primarily a $303,000 (18.3%) increase in occupancy expense to $1,962,000 that included $238,000 of accelerated depreciation expense of leasehold improvements related to the closing of two branches in the quarter ended March 31, 2014, a $255,000 (58%) reduction in reversal of provision for losses on unfunded commitments to $185,000 from $440,000, a $228,000 (44.8%) increase in professional fees to $739,000 that included $296,000 of legal and consulting fees related to the proposed merger with North Valley, a $147,000 (29.6%) increase in ATM network charges to $643,000, and a $100,000 (9.3%) increase in data processing and software expense.

TriCo’s unaudited consolidated financial statements for the quarter ended March 31, 2014 will be included in TriCo’s Quarterly Report on Form 10-Q for the year ended March 31, 2014, which will be filed with the SEC and incorporated by reference into this joint proxy statement/prospectus.

North Valley Results for Quarter Ended March 31, 2014 (Unaudited)

North Valley reported net income for the quarter ended March 31, 2014 of $919,000, or $0.13 per diluted share compared to net income for the quarter ended March 31, 2013 of $1,261,000, or $0.18 per diluted share.

North Valley did not record a provision for loan losses for the quarters ended March 31, 2014 and 2013. The allowance for loan losses at March 31, 2014 was $9,058,000, or 1.78% of total loans, compared to $9,301,000, or 1.83% of total loans, at December 31, 2013 and $9,651,000, or 1.98% of total loans, at March 31, 2013.

At March 31, 2014, North Valley’s total assets were $918,972,000, an increase of $8,238,000, or 0.9%, from $910,734,000 at March 31, 2013. The loan portfolio totaled $508,056,000 at March 31, 2014, an increase of $19,450,000, or 4.0%, compared to $488,606,000 at March 31, 2013. The loan to deposit ratio at March 31, 2014 was 64.7% as compared to 63.0% at March 31, 2013, and 64.6% at December 31, 2013. Total deposits increased $9,897,000, or 1.3%, to $785,817,000 at March 31, 2014 compared to $775,920,000 at March 31, 2013. Available-for-sale investment securities totaled $273,143,000 at March 31, 2014, a decrease of $10,578,000 from the total at March 31, 2013. When compared to December 31, 2013, total assets increased $1,208,000 from $917,764,000, while loans decreased by $1,188,000 from $509,244,000, and deposits decreased $2,032,000 from $787,849,000. Available-for-sale investment securities decreased $6,336,000 from December 31, 2013 to March 31, 2014, while Federal funds sold increased $6,615,000 from December 31, 2013 to March 31, 2014.

Nonperforming loans (defined as nonaccrual loans and loans 90 days or more past due and still accruing interest) decreased $1,644,000, or 25.5%, to $4,805,000 at March 31, 2014 from $6,449,000 at March 31, 2013, and decreased $288,000 from the December 31, 2013 balance of $5,093,000. Nonperforming loans as a percentage of total loans were 0.95% at March 31, 2014, as compared to 1.00% at December 31, 2013 and 1.32% at March 31, 2013.

During the first quarter of 2014, North Valley identified five loans totaling $1,669,000 as additional nonperforming loans. The additions were offset by reductions in nonperforming loans totaling $1,957,000 due primarily to the transfer of one property to Other Real Estate Owned (“OREO”) totaling $1,231,000, and secondarily to collections received on certain loans and charge-offs. Of the five loans totaling $1,669,000 identified as nonperforming loans during the first quarter of 2014, two relationships make up $1,526,000 of the balance. The first relationship is for a commercial real estate loan totaling $865,000 located in Stanislaus County. There is no specific reserve required for this loan. The second relationship consists of two loans totaling $661,000 for residential income property located in Solano County. North Valley has recorded a $215,000 charge-off for these loans and there is no specific reserve required. The remaining two loans of the five identified as nonperforming loans in the first quarter total $143,000. Charge-offs of $34,000 were recorded against one of the loans and there were no specific reserves required.

Gross loan charge offs for the first quarter of 2014 were $298,000 and recoveries totaled $55,000 resulting in net charge offs of $243,000. Gross loan charge offs for the first quarter of 2013 were $1,056,000 and recoveries totaled $249,000 resulting in net charge offs of $807,000.

Nonperforming assets (nonperforming loans and OREO) totaled $7,438,000 at March 31, 2014, a decrease of $20,376,000 from the March 31, 2013 balance of $27,814,000, and a $1,109,000 decrease from the December 31, 2013 balance of $8,547,000. Nonperforming assets as a percentage of total assets were 0.81% at March 31, 2014 compared to 3.05% at March 31, 2013 and 0.93% at December 31, 2013.

North Valley’s OREO properties decreased $821,000 to $2,633,000 at March 31, 2014 from $3,454,000 at December 31, 2013. The decrease in OREO was due to the sale of three properties totaling $2,227,000 (a gain of $175,000 was recorded on the sale), which was partially offset by the transfer of one property to OREO totaling $1,231,000. Subsequent to March 31, 2014, North Valley sold an OREO property located in Shasta County at its recorded value of $2,154,000 resulting in no loss on the sale. The transaction closed on April 4, 2014.

Net interest income, which represents North Valley’s largest component of revenues and is the difference between interest earned on loans, investments and other earning assets and interest paid on deposits and borrowings, increased $326,000, or 4.4%, for the three months ended March 31, 2014 compared to the same period in 2013. Interest income increased by $251,000, or 3.2%, primarily due to an increase in average earning asset balances. The Company had foregone interest income of $10,000 and $85,000 for the loans on nonaccrual status for the three months ended March 31, 2014 and 2013, respectively. Average loans increased $22,734,000 in the first quarter of 2014 compared to the first quarter of 2013, while the yield on the loan portfolio decreased 22 basis points to 5.11% for the quarter ended March 31, 2014. Interest expense decreased $75,000, or 17.4%, due primarily to a decrease in the rates paid on deposits for the quarter ended March 31, 2014 compared to the same period in 2013. Overall, average earning assets increased $41,029,000 to $838,890,000 in the first quarter of 2014 compared to the first quarter of 2013. Average yields on earning assets decreased 9 basis points from the quarter ended March 31, 2013, to 3.94% for the quarter ended March 31, 2014 while the average rate paid on interest-bearing liabilities decreased by 5 basis points to 0.23%. North Valley’s net interest margin for the quarter ended March 31, 2014 was 3.77%, a decrease of 4 basis points from the margin of 3.81% for the first quarter in 2013 and an increase of 6 basis points from the 3.71% net interest margin for the linked quarter ended December 31, 2013.

Noninterest income for the quarter ended March 31, 2014 decreased $1,899,000, or 43.9%, to $2,430,000 compared to $4,329,000 for the same period in 2013. Service charges on deposits decreased by $254,000 to $698,000 for the first quarter of 2014 compared to $952,000 for the same period in 2013. Other fees and charges decreased by $108,000 to $1,012,000 for the first quarter of 2014 compared to $1,120,000 for the first quarter of 2013. North Valley recorded gains on the sale of mortgage loans of $184,000, and gains on the sale of SBA loans of $45,000 for the first quarter of 2014 compared to gains of $757,000 and $168,000, respectively, for the same period in 2013. North Valley did not record a gain on the sale of investment securities for the first quarter of 2014 compared to gains on the sale of investment securities of $543,000 for the same period in 2013. Other noninterest income decreased $298,000, to $491,000 for the quarter ended March 31, 2014 compared to $789,000 for the same period in 2013.

Noninterest expense decreased $1,132,000, or 11.5%, to $8,756,000 for the first quarter of 2014 from $9,888,000 for the first quarter in 2013. Salaries and employee benefits decreased $139,000, for the first quarter of 2014 compared to the first quarter of 2013. Occupancy and furniture and equipment expense decreased $14,000 for the first quarter of 2014 compared to the first quarter of 2013, OREO expense decreased $366,000 to $10,000, for the first quarter of 2014 compared to $376,000 for the same period in 2013, and FDIC and state assessments decreased $77,000 to $141,000 for the first quarter of 2014, compared to $218,000 for the same period in 2013. Other expense decreased $536,000 to $2,743,000 for the first quarter of 2014 compared to $3,279,000 for the same period in 2013. For the three months ended March 31, 2014, North Valley had approximately $290,000 of merger related expenses resulting from the pending merger with TriCo Bancshares, included in other noninterest expenses.

North Valley recorded a provision for income taxes for the quarter ended March 31, 2014 of $517,000, resulting in an effective tax rate of 36.0%, compared to a provision for income taxes of $616,000, or an effective tax rate of 32.8%, for the quarter ended March 31, 2013.

North Valley’s unaudited consolidated financial statements for the quarter ended March 31, 2014 will be included in its Quarterly Report on Form 10-Q for the quarter ended March 31, 2014, which will be filed with the SEC and incorporated by reference into this joint proxy statement/prospectus.

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RISK FACTORS

In addition to the other information contained in or incorporated by reference into this joint proxy statement/prospectus,transactions contemplated therein, including the matters addressed under the caption entitled “Cautionary Statement Regarding Forward-Looking Statements,” North Valley shareholders should carefully consider the following risk factors in deciding whether to vote for approval of the merger and approval and adoption of the merger agreement, and TriCo shareholders should carefully consider the following risks in deciding whether to vote for approval of the merger and approval and adoption of the merger agreement and approval of the issuance of the shares of TriCo common stock in connection with the merger. North Valley andmerger, which we refer to as the TriCo should also considermerger proposal. If you are an FNBB shareholder, you are being asked to vote (1) to approve the other information in this documentmerger agreement and the other documents incorporated by reference into this document. Please seemerger, which we refer to as the sections entitled “Where You Can Find More Information” beginningFNBB merger proposal, and (2) to approve on page van advisory(non-binding) basis, the compensatory arrangements between FNBB and “Incorporationits named executive officers providing for compensation in connection with the merger and the agreements and understandings pursuant to which such compensation may be paid or become payable. As a result of Certain Documents by Reference” beginning on page 156.

Because the market pricemerger, FNBB will cease to exist and FNBB shareholders will have the right to receive in exchange for each of their shares of common stock of FNBB, or FNBB common stock, the merger consideration consisting of 0.98 shares of TriCo common stock, will fluctuate,or the valueexchange ratio, as further described in “The Merger—The Merger Consideration” beginning on page [●].

Each of the TriCo and FNBB shareholders is also being asked to consider and vote upon a proposal to grant discretionary authority to adjourn the special meeting of their respective shareholders, if necessary, to permit further solicitation of proxies if there are not sufficient votes at the time of either or both special meetings to approve the matters being presented at such special meetings.

In addition to receiving the necessary regulatory approvals, the merger considerationcannot be completed unless the TriCo shareholders vote to approve the TriCo merger proposal and FNBB shareholders vote to approve the FNBB merger proposal. At each of the respective shareholders’ meetings, TriCo and FNBB shareholders will vote on the proposals necessary to complete the merger. Information about these shareholders’ meetings, the merger agreement and the merger and the other business to be receivedconsidered by North Valley shareholders may change.at each of the shareholders’ meetings is contained in this document.

Upon completionThis document constitutes both a joint proxy statement of TriCo and FNBB and a prospectus of TriCo. It is a joint proxy statement because each of the boards of directors of TriCo and FNBB is soliciting proxies using this document for their respective shareholder meetings. It is a prospectus because TriCo, in connection with the merger, is offering shares of TriCo common stock in exchange for outstanding shares of FNBB common stock in the merger.

Q: What will FNBB Shareholders Receive in the Merger?

A: In the merger, each share of North ValleyFNBB common stock (including the associated preferred stock purchase rights issued pursuant to the Amended and Restated Shareholder Protection Rights Agreement dated as of March 26, 2009, as amended, between North Valley and Computershare, Inc., as Rights Agent)owned by an FNBB shareholder will be converted into the merger consideration consisting of a fraction of a shareright to receive 0.98 shares of TriCo common stock pursuant to the terms of the merger agreement. The exchange ratio will not be adjusted for changes in the market price of TriCo or North Valley common stock prior to the closing. The closing price of TriCo common stockbased on the date that the merger is completed may vary fromexchange ratio.

Based on the closing price of TriCo common stock on December 11, 2017, the date TriCo and North Valley announcedvalue of the per share merger consideration payable to holders of FNBB common stock was $40.51. Based on the date that this document is being mailed to each of the TriCo and North Valley shareholders, and on the date of the shareholders’ meeting of TriCo and North Valley shareholders. Any change in the marketclosing price of TriCo common stock prior to completionon [●], 2018, the last practicable date before the date of the merger may affectthis joint proxy statement/prospectus, the value of the per share merger consideration that North Valley shareholders will receive upon completionpayable to holders of FNBB common stock was $[●].

Q: Is the merger. Stock price changes may result from a variety of factors, including general market and economic conditions, changes in our respective businesses, operations and prospects, and regulatory considerations, among other things. Many of these factors are beyondexchange ratio subject to change?

A: Yes. While the control of TriCo and North Valley. North Valley shareholders should obtain current market quotations forexchange ratio is generally fixed at 0.98 shares of TriCo common stock, before voting their shares at the North Valley special meeting.

North Valley shareholders will have a reduced ownership and voting interest after the merger and will exercise less influence over management.

North Valley shareholders currently have the right to voteagreement includes a trading collar that could result in the election of the board of directors of North Valley and on other matters affecting North Valley. Upon the completiontermination of the merger each North Valley shareholder who receivesagreement or a change to the exchange ratio. In particular, TriCo can elect to terminate the merger agreement if both (i) the average share price of TriCo common stock for the20-day period up to and including the fifth day prior to the closing date of the merger (the “TriCo average closing price”) is greater than $49.78, which equals 120% of the average share price of TriCo common stock for the 20trading-day period up to and including December 8, 2017, which was $41.48, which we refer to as the “initial TriCo trading price”, and (ii) TriCo common stock outperforms the KBW Nasdaq Regional Banking Index by more than 20% since December 8, 2017, unless FNBB agrees to decrease the exchange ratio to cure the deficiency so that fewer shares of TriCo common stock will becomebe issued to FNBB shareholders on a shareholderper share basis. Conversely, FNBB can terminate the merger agreement if both (i) the TriCo average closing price is less than $33.18, which equals 80% of the initial TriCo trading price, and (ii) TriCo common stock underperforms the KBW Nasdaq Regional Banking Index by more than 20%, unless TriCo agrees to increase the exchange ratio to cure the deficiency so that more shares of TriCo withcommon stock will be issued to FNBB shareholders on a percentage ownershipper share basis.

If the average closing share price of TriCo thatcommon stock is smaller$33.18 or more and $49.78 or less, the exchange ratio will remain unchanged at 0.98 shares of TriCo common stock. For more information concerning the potential change to the exchange ratio, see “The Merger—The Merger Consideration—Potential Adjustment to Exchange Ratio” on page [●].

Q: How will the parties decide whether to adjust the exchange ratio or allow the merger agreement to terminate?

A: If TriCo elects to terminate the merger agreement because the TriCo average closing price is greater than such shareholder’s percentage ownership of North Valley. It is currently expected that$49.78 and TriCo common stock outperforms the former shareholders of North ValleyKBW Nasdaq Regional Banking Index by more than 20%, FNBB can elect to prevent the termination by allowing the exchange ratio to adjust downward as a group will receive sharesprovided in the merger constituting approximately 28.6%agreement. FNBB’s board of directors would decide whether FNBB will make this election. Conversely, if FNBB elects to terminate the merger agreement because the TriCo average closing price is less than $33.18 and TriCo common stock underperforms the KBW Nasdaq Regional Banking Index by more than 20%, TriCo can elect to prevent the termination by allowing the exchange ratio to adjust upward as provided in the merger agreement. TriCo’s board of directors would decide whether TriCo will make this election. The boards of directors of TriCo and FNBB will evaluate various factors at the time of closing in determining whether to exercise any termination rights TriCo and FNBB may have and whether to prevent any termination by allowing the exchange ratio to adjust. Following the time of closing, TriCo will file a Current Report on Form8-K with the SEC that will disclose the exchange ratio that will apply in the merger.

Q: Will FNBB shareholders be able to trade the TriCo common stock that they receive in the merger?

A: Yes. The TriCo common stock issued in the merger to FNBB shareholders will be listed on the Nasdaq Global Select Market under the symbol “TCBK.” Unless you are deemed an “affiliate” of TriCo, you may sell or transfer the shares of TriCo common stock you receive in the merger without restriction.

Q: Why is my vote important?

A: The TriCo merger proposal must be approved by the holders of a majority of the outstanding shares of TriCo common stock immediately afterand the merger. BecauseFNBB merger proposal must be approved by the holders of this, North Valleya majority of the outstanding shares of FNBB common stock. We cannot complete the merger without these shareholder approvals. TriCo shareholders may have less influencewill vote on the managementapplicable proposals necessary to complete the merger at the TriCo special meeting and policies of TriCo than they now havethe FNBB shareholders will vote on the managementapplicable proposals necessary to complete the merger at FNBB special meeting. Information about the TriCo special meeting and policiesthe FNBB special meeting, the merger and the other business to be considered by shareholders at each of North Valley.the special meetings is contained in this document.

The market price forIf you are a TriCo or FNBB shareholder and you do not vote, it will have the same effect as a vote against the merger agreement. Holders of [●] shares of FNBB common stock, may be affected by factors different from those that historicallyrepresenting approximately 20% of the outstanding shares of FNBB common stock, have affected North Valley.

Upon completionsigned shareholder agreements with TriCo agreeing to vote in favor of the merger holdersagreement.

Q: Why must the TriCo shareholders approve the merger agreement and the issuance of North Valley common stock will become holdersshares of TriCo common stock. TriCo’s business differs from that of North Valley, and accordingly the results of operations of TriCo will be affected by some factors that are different from those currently affecting the results of operations of North Valley. For a discussion of the business of TriCo and North Valley and some important factors to considerstock in connection with the business, seemerger?

A: TriCo shareholders are required to approve the section entitled “Information About the Companies” beginning on page 28merger agreement and the documents incorporated by reference in this joint proxy statement/prospectus and referred to under the section entitled “Where You Can Find More Information” beginning on page v.

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TriCo may fail to realize the anticipated benefitsissuance of shares of the merger.