As filed with the Securities and Exchange Commission on April 10, 2020December 5, 2022

RegistrationNo. 333-235690333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 1

TO

FORMS-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Sientra, Inc.

(Exact name of registrant as specified in its charter)

420 South Fairview Avenue, Suite 200

Santa Barbara, CA 93117

(805)562-3500

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Jeffrey Nugent

Ronald Menezes

Chief Executive Officer

Sientra, Inc.

420 South Fairview Avenue, Suite 200

Santa Barbara, CA 93117

(805)562-3500

(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: From time to time after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, 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, please 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(c) 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 registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ☐

If this form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, anon-accelerated filer, a smaller reporting company or an emerging growth company. See definition of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule12b-2 of the Exchange Act.

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 Securities Act.  ☐

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, as amended, 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.

EXPLANATORY NOTE

Pursuant to Rule 429 under the Securities Act, the prospectus (the “Prospectus”) included in this registration statement on Form S-3 (the “Registration Statement”) is a combined prospectus relating to this Registration Statement and to the registration statement on Form S-3 (No. 333-237636), previously filed by Sientra, Inc. on April 10, 2020, and declared effective on May 7, 2020 (the “Initial Registration Statement”), which relates to the offer and resale of up to an aggregate of 14,634,147 shares of common stock issuable upon exercise of outstanding warrants, previously issued to the selling stockholders named therein. This Registration Statement, which is a new registration statement, combines the 14,634,147 shares of common stock from the Initial Registration Statement, with an additional 53,946,718 shares of common stock issuable upon exercise of outstanding warrants, all of which are registered hereby for offer and resale by the selling stockholders named in the Prospectus, to enable an aggregate of 68,580,865 shares of common stock to be offered pursuant to the combined prospectus. Pursuant to Rule 429 under the Securities Act, this Registration Statement also constitutes a post-effective amendment to the Initial Registration Statement (the “Post-Effective Amendment”), and such Post-Effective Amendment shall hereafter become effective concurrently with the effectiveness of this Registration Statement in accordance with Section 8(c) of the Securities Act.

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

Subject to completion, dated April 10, 2020December 5, 2022

PROSPECTUS

SIENTRA, INC.

607,44268,580,865 Shares

Common Stock

This prospectus relates to an aggregatethe resale or other disposition from time to time of up to 607,442to:

We will not receive any of the proceeds from any sale of our common stock by the selling stockholder.

In November 2019, we entered into an asset purchase agreement (Purchase Agreement) with Vesta. Pursuant to the Purchase Agreement, we purchased certain assets, assumed certain liabilities and obtained a non-exclusive, royalty-free, perpetual, irrevocable, assignable, sublicensable, and worldwide license to certain intellectual property owned by Vesta. As part of the consideration, we agreed that, in the event the closing price of our common stock equals or exceeds a certain agreed upon price target (First Milestone Price Target) on any date through November 7, 2023, we will issue Vesta 303,721 shares of common stock (First Milestone Shares) within five business days of such date, and in the event the closing price of our common stock equals or exceeds a certain agreed upon price target (Second Milestone Price Target) on any date through November 7, 2023, we will issue Vesta 303,721 shares of common stock (Second Milestone Shares) within five business days of such date. We refer to the First Milestone Shares and the Second Milestone shares together as the Shares.

The Shares are subject to a contractuallock-up on transfers for a period continuing to and including May 7, 2021 and November 7, 2022 for the First Milestone Shares and Second Milestone Shares, respectively. In addition, thelock-up restricts Vesta from selling more thanone-third of the First Milestone Shares or Second Milestone Shares in any thirty day period. For more information, refer to the section of this prospectus entitled “Selling Stockholder.”

The selling stockholder may offer shares of our common stock from time to time in a number of different ways and at varying prices. For more information on possible methods of offer and sale by the selling stockholder, refer to the section of this prospectus entitled “Plan of Distribution.” If any underwriters, dealers or agents are involved in the sale of any of the shares of common stock, their names, and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. We have agreed to bear all of the expenses (other than underwriting discounts and commissions) incurred in connection with the registration of these shares. The selling stockholder will pay or assume brokerage commissions and similar charges incurred for the sale of shares of our common stock.

The information in this prospectus is accurate as of the date on the front cover. Information incorporated by reference into this prospectus is accurate as of the date of the document from which the information is incorporated.

You should not assume that information contained in or incorporated by reference into this prospectus is accurate as of any other date.

Our common stock is listed on the NASDAQNasdaq Global Select Market under the symbol “SIEN.” On April 9, 2020December 1, 2022 the closing price of our common stock was 1.98$0.29 per share.

Investing in our securities involves risks. See the section of this prospectus entitled “Risk Factors” and contained in any applicable prospectus supplement and any related free writing prospectus and under similar sections in the other documents that are incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is                , 20202022

TABLE OF CONTENTS

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ABOUT THIS PROSPECTUS

This prospectus is a part of a registration statement that we filed with the Securities and Exchange Commission (SEC) utilizing a “shelf” registration process. This prospectus relates to the possible resale by the selling stockholder of an aggregate of up to 607,44268,580,865 shares of our common stock from time to time in one or more offerings.

The selling stockholder may offer and sell, from time to time, an aggregate of up to 607,44268,580,865 shares of our common stock under the prospectus. In some cases,If necessary, the selling stockholder will also be required to provide a prospectus supplement containing specific information aboutmanner in which the selling stockholder and the terms on which they are offering and sellingshares of our common stock.stock may be offered and sold will be described in a supplement to this prospectus. We may also add, update or change in a prospectus supplement any information contained in this prospectus. To the extent that any statement made in a prospectus supplement is inconsistent with statements made in this prospectus, the statements made in this prospectus will be deemed modified or superseded by those made in the prospectus supplement. Before you make any investment decision, you should read this prospectus, any accompanying prospectus supplement, any post-effective amendments to the registration statement of which this prospectus is a part, the documents incorporated by reference in such registration statement, and the additional information described under “Where You Can Find More Information; IncorporationAdditional Information.”

You should rely only on the information that we have provided or incorporated by Reference.”

Neitherreference in this prospectus, any applicable prospectus supplement and any related free writing prospectus that we nor the selling stockholdermay authorize to be provided to you. We have not authorized any broker, dealer, salesman or other person to give any information or to make any representation other than those contained or incorporated by reference in this prospectus, and any accompanyingapplicable prospectus supplement.supplement or any related free writing prospectus that we may authorize to be provided to you. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus, or anythe accompanying prospectus supplement. supplement or related free writing prospectus. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted.

This prospectus, the accompanying supplement to this prospectus and any accompanyingrelated free writing prospectus, supplementif any, do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus, andthe accompanying supplement to this prospectus or any accompanyingrelated free writing prospectus, supplementif any, constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus, and any accompanyingapplicable prospectus supplement or any related free writing prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference therein is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus, and any accompanyingapplicable prospectus supplement or any related free writing prospectus is delivered or the applicable securities are sold on a later date. Our business, financial condition, results of operations and prospects may have changed since those dates.

“Sientra”, “Sientra Platinum20”, “Sientra Full Circle”, “OPUS”“Sientra Smooth”, “Sientra Teardrop”, “Allox”, “Allox2”, “Anatomical Controlled”, “BIOCORNEUM”, “Curve”, “Dermaspan”, “Luxe”, “Softspan”, “Silishield”, “miraDry”“AuraGen”, “Miramar Labs”“AuraGen 1-2-3”, “miraDry“AuraSorb” and Design”, “miraDry Fresh”, “bioTip”, “The Sweat Stops Here”, “No Sweat No Stress”, “Sweat Less Live More”, “Drop Design”, “miraWave”, “miraSmooth”, “miraFresh”, “freshRewards”, “freshNet”, “freshEquity”, and “ML Stylized mark”“AuraClens” are trademarks of our company. Our logo and our other trade names, trademarks and service marks appearing in this document are our property. Other trade names, trademarks and service marks appearing in this document are the property of their respective owners. Solely for convenience, our trademarks and trade names referred to in the document, appear without the TM or the (R) symbol, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights, or the rights of the applicable licensor to these trademarks and trade names.names

RISK FACTORS

Investment in our securities involves risks. Prior to making a decision about investing in our securities, you should consider carefully all of the information included and incorporated by reference or deemed to be incorporated by reference in this prospectus or the applicable prospectus supplement, including the risk factors incorporated by reference herein from our Annual Report on Form10-K for for the year ended December 31, 2018,2021, as supplementsupplemented by our Quarterly Reports on Form10-Q for for the quarters ended March 31, 2019,2022, June 30, 20192022, and September 30, 2019,2022, as updated by annual, quarterly and other reports and documents we file with the Securities and Exchange Commission, or the SEC, after the date of this prospectus and that are incorporated by reference herein or in the applicable prospectus supplement. Each of these risk factors could have a material adverse effect on our business, results of operations, financial position or cash flows, which may result in the loss of all or part of your investment.

A pandemic, epidemic or outbreak of an infectious disease, such as COVID-19, or coronavirus, may materially and adversely affect our business, our operations and our financial results.

The recent outbreak of COVID-19 originated in Wuhan, China, in December 2019 and has since spread to multiple countries, including the United States. On March 11, 2020, the World Health Organization declared COVID-19 a pandemic. Pandemics, like COVID-19, or other outbreaks of infectious disease may result in a period of business disruption, including reduced sales as patients might cancel or defer elective procedures or otherwise avoid medical facilities, resulting in reduced patient volumes and operating revenues. For example, the spread of COVID-19 has resulted in travel restrictions which impact medical tourism and our sales professionals’ ability to travel. In addition, hospitals may limit access for non-patients, including our sales professionals, which could negatively impact our access to physicians. A significant percentage of our products are utilized in elective surgeries or procedures, which may be deferred or avoided altogether due to COVID-19 outbreak. Governmental agencies and hospital administrators may also instruct hospitals to postpone some elective procedures in preparation for COVID-19-related hospitalizations. The spread of COVID-19, or another infectious disease, could also result in delays or disruptions in our supply chain or adversely affect our manufacturing facilities and personnel. The COVID-19 outbreak continues to be fluid and uncertain, making it difficult to forecast the final impact it could have on our future operations or financial results.

USE OF PROCEEDS

We will not receive any of the proceeds from the sale or other disposition of shares of our common stock by the selling stockholdersstockholder pursuant to this prospectus.

DESCRIPTION OF CAPITALCOMMON STOCK

The following description of our capitalcommon stock together with any additional information we include in any applicable prospectus supplements or any free writing prospectuses that we may authorize to be delivered to you, summarizes the material terms and provisions of our capitalcommon stock that wethe selling stockholder may offer under this prospectus. While the terms we have summarized below will apply generally to any future capital stock that we may offer, we will describe the particular terms of any class or series of these securities in more detail in the applicable prospectus supplement or free writing prospectus. For the complete terms of our capitalcommon stock, please refer to our certificate of incorporation and our bylaws that are incorporated by reference into the registration statement of which this prospectus is a part or may be incorporated by reference in this prospectus or any prospectus supplement. The terms of these securitiesour common stock may also be affected by the Delaware General Corporation Law, or the DGCL. The summary below and that contained in any prospectus supplement or free writing prospectus are qualified in their entirety by reference to our certificate of incorporation and our bylaws.

Common Stock

We are authorized to issue 200,000,000 shares of common stock, of which 49,534,414100,995,909 shares were issued and outstanding as of September 30, 2019.November 10, 2022. The holders of common stock possess exclusive voting rights in us, except to the extent our board of directors specifies voting power with respect to any other class of securities issued in the future. Each holder of our common stock is entitled to one vote for each share held of record on each matter submitted to a vote of stockholders, including the election of directors. Stockholders do not have any right to cumulate votes in the election of directors.

Subject to preferences that may be granted to the holders of preferred stock, each holder of our common stock is entitled to share ratably in distributions to stockholders and to receive ratably such dividends as may be declared by our board of directors out of funds legally available therefor. In the event of our liquidation, dissolution or winding up, the holders of our common stock will be entitled to receive, after payment of all of our debts and liabilities and of all sums to which holders of any preferred stock may be entitled, the distribution of any of our remaining assets. Holders of our common stock have no conversion, exchange, sinking fund, redemption or appraisal rights (other than such as may be determined by our board of directors in its sole discretion) and have no preemptive rights to subscribe for any of our securities.

All of the outstanding shares of our common stock are, and the shares of common stock issued upon the conversion of any securities convertible into our common stock will be, fully paid andnon-assessable. The shares of common stock offered by this prospectus or upon the conversion of any preferred stock or debt securities or exercise of any warrants offered pursuant to this prospectus, when issued and paid for, will also be, fully paid andnon-assessable.

Our common stock is listed on the Nasdaq Global Select Market under the symbol “SIEN.”

Preferred Stock

We are authorized to issue 10,000,000 shares of preferred stock, none of which were issued and outstanding as of September 30, 2019. Our board is authorized to classify or reclassify any unissued portion of our authorized shares of preferred stock to provide for the issuance of shares of other classes or series, including preferred stock in one or more series. We may issue preferred stock from time to time in one or more classes or series, with the exact terms of each class or series established by our board. Without seeking stockholder approval, our board may issue preferred stock with voting and other rights that could adversely affect the voting power of the holders of our common stock. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of the common stock.

the business combination or the acquisition of shares that resulted in a stockholder becoming an interested stockholder is approved in a prescribed manner. Generally, a “business combination” includes a merger, asset or stock sale or other transaction resulting in a financial benefit to the interested stockholder. Generally, an “interested stockholder” is a person who, together with affiliates and associates, owns (or within three years prior to the determination of interested stockholder status did own) 15% or more of a corporation’s voting stock. The existence of this provision would be expected to have an anti-takeover effect with respect to transactions not approved in advance by our board of directors, including discouraging attempts that might result in a premium over the market price for the shares of common stock held by our stockholders.

Classified Board

Our certificate of incorporation and our bylaws provide that our board of directors is divided into three classes, each comprised of, threeas nearly as possible, one-third of the total number of directors. The directors designated as a Class I directors have a term expiring at our

Requirements for Advance Notification of Stockholder Nominations and Proposals

Our bylaws establish advance notice procedures with respect to stockholder proposals and nomination of candidates for election as directors other than nominations made by or at the direction of our board of directors or a committee of our board of directors.

No Cumulative Voting

The DGCL provides that stockholders are denied the right to cumulate votes in the election of directors unless our certificate of incorporation provides otherwise. Our certificate of incorporation does not provide for cumulative voting.

SELLING STOCKHOLDER

This prospectus relates to the possible resale distribution or other transfer by Vesta, from time to time of an aggregate of up to 607,44268,580,865 shares of our common stock.

Acquisition of Shares by the Selling Stockholder

On November 7, 2019 (the “Closing Date”), we entered into an Asset Purchase Agreement (the “Purchase Agreement”) with Vesta,stock issuable or potentially issuable pursuant to which we purchased certain assets, assumed certain liabilities and obtained anon-exclusive, royalty-free, perpetual, irrevocable, assignable, sublicensable, and worldwide license to certain intellectual property owned by Vesta (the “Vesta Acquisition”). In partial consideration of the Vesta Acquisition, we agreed that, inConvertible Notes, the event the closing price of our common stock equals or exceeds a certain agreed upon price target (the “First Milestone Price Target”) on any date through November 7, 2023, we will issue Vesta 303,721 shares of common stock (the “First Milestone Shares”) within five business days of such date, and in the event the closing price of our common stock equals or exceeds a certain agreed upon price target (the “Second Milestone Price Target”) on any date through November 7, 2023, we will issue Vesta 303,721 shares of common stock (the “Second Milestone Shares”) within five business days of such date.

The Shares are subject to a contractuallock-up on transfers for a period continuing to and including May 7, 2021 and November 7, 2022 for the First Milestone Shares and Second Milestone Shares, respectively. In addition, thelock-up restricts Vesta from selling more thanone-third of the First Milestone Shares or Second Milestone Shares in any thirty day period.

Pursuant to the Purchase Agreement, we are required to use our commercially reasonable efforts to file and maintain a resale registrations statement registering the resale of the First Milestone SharesWarrants and the Second Milestone Shares.

Selling StockholderExchange Warrants.

The following table presents information regarding the selling stockholder, and the shares of common stock that itthey may offer and sell or otherwise dispose of from time to time under this prospectus. This table is prepared based on information supplied to us by the selling stockholder.stockholder as of October 12, 2022. As used in this prospectus, the term “selling stockholder” includes Vesta Intermediate Funding, Inc., and any donees, pledgees,pledges, transferees permitted assigns or other successors in interest selling shares received after the date of this prospectus from a selling stockholder as a gift, pledge, distribution or other non-sale related transfer.

The number of shares in the column “Number of Shares Being Offered” represents all of the shares that the selling stockholder may offer and sell, distribute or otherwise transfer under this prospectus. The selling stockholder may sell distribute or otherwise transfer some, all or none of its shares.their respective shares of common stock. We do not know how long the selling stockholder will hold thetheir respective shares before selling distributing or otherwise transferring them, and except as described above, we currently have no agreements, arrangements or understandings with the selling stockholder regarding the sale of any of the shares. Because

Beneficial ownership is determined in accordance with Rule 13d-3(d) promulgated by the selling stockholder may offer all, some, or noneSEC under the Securities Exchange Act of the shares of common stock that it owns pursuant to this offering, we cannot estimate the number1934, as amended.

The percentages of shares of common stock that the selling stockholder will hold after completion of the offering. For purposes of this table, we have assumed that the selling stockholder will have sold all of the shares covered by this prospectus upon the completion of the applicable offering.

PLAN OF DISTRIBUTION

The selling stockholder, including donees, pledgees, transferees, permitted assigns or other successors in interest (including transferees that receive shares of common stock from the selling stockholder under this prospectus), may use any one or more of the following methods (or in any combination) to sell, distribute or otherwise transfer the securities from time to time:

In particular, the selling stockholder may offer and sell, distribute or otherwise transfer from time to time at a fixed price or prices, which may be changed; at market prices prevailing at the time of sale; at prices related to prevailing market prices; at varying prices determined at the time of sale; or at negotiated prices. These offers and sales or distributiondistributions may be effected from time to time in one or more transactions, including:

The selling stockholder may also sell shares in open market transactions under Rule 144 under the Securities Act, if available, rather than under this prospectus.

entered into with the selling stockholder to indemnification by the selling stockholder against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which such agents, dealers or underwriters may be required to make in respect thereof. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services on the selling stockholder’sstockholder’ behalf.

At any time a particular offer of the shares of common stock is made, a prospectus supplement, if required, will be distributed and set forth the terms of each specific offering, including the name or names of any underwriters or agents, the purchase price of the shares of common stock and the proceeds to the selling stockholder from such sales or distribution, any delayed delivery arrangements, any underwriting discounts and other items constituting underwriters’ compensation, any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers. Any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time.

LEGAL MATTERS

The validity of the securities offered by this prospectus will be passed upon for us by DLA Piper LLP (US), San Diego, California.

EXPERTS

The consolidated financial statements and the related financial statement schedule, of Sientra, Inc. as of December 31, 20192021 and 2018,2020, and for each of the years in the three-year period ended December 31, 2019, and management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 20192021, have been incorporated by reference herein, and in the registration statement, in reliance upon the reportsreport of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The audit report covering the December 31, 2019 financial statements refers to a change in the method of accounting for leases effective January 1, 2019 due to the adoption of the Accounting Standards Update, Leases (Topic 842).

The audit report on the effectiveness of internal control over financial reporting as of December 31, 2019, contains an explanatory paragraph that states the Company acquired certain assets from Vesta Intermediate Funding, Inc. (Vesta) during 2019 and management excluded from its assessment of the effectiveness of the Company’s internal control over financial reporting as of December 31, 2019, Vesta’s internal control over financial reporting associated with total assets of $21.3 million included in the consolidated financial statements of the Company as of and for the year ended December 31, 2019. The audit report on the on the effectiveness of internal control over financial reporting also excluded an evaluation of the internal control over financial reporting of Vesta.

The audit report on the effectiveness of internal control over financial reporting as of December 31, 2019, expresses an opinion that Sientra, Inc. did not maintain effective internal control over financial reporting as of December 31, 2019 because of the effect of a material weakness on the achievement of the objectives of the control criteria and contains an explanatory paragraph that states the control environment was ineffective in holding individuals accountable for the operation of their internal control responsibilities. This control failure prevented the effective operation of controls over goodwill and intangible asset impairment, including the underlying financial data, calculations and assumptions supporting the forecasted financial information utilized to measure the fair value of the reporting unit, intangible assets, and the associated impairment charges.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We are a reporting company and file annual, quarterly and current reports, proxy statements and other information with the SEC. We have filed with the SEC a registration statement on FormS-3 under under the Securities Act with respect to the securities we are offering under this prospectus. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. The SEC maintains an internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, where our SEC filings are also available. The address of the SEC’s web site is http://www.sec.gov. We maintain a website at http://www. http://sientra.com.www.sientra.com. Information contained in or accessible through our website does not constitute a part of this prospectus.

We will provide each person, including any beneficial owner, to whom a prospectus is delivered, a copy of any or all of the information that has been incorporated by reference into this prospectus but not delivered with this prospectus upon written or oral request at no cost to the requester. Requests should be directed to: Sientra, Inc., 420 South Fairview Avenue, Suite 200, Santa Barbara, CA 93117, Telephone: (805)562-3500.

607,44268,580,865 Shares

Common Stock

Prospectus

            , 20202022

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth the various expenses to be incurred in connection with the registration of the securities being registered hereby, all of which will be borne by the registrant.

Item 15. Indemnification of Officers and Directors

Section 145 of the DGCL authorizes a court to award or a corporation’s board of directors to grant indemnification to directors and officers in terms sufficiently broad to permit such indemnification under certain circumstances for liabilities (including reimbursement for expenses incurred) arising under the Securities Act of 1933, as amended, or the Securities Act.

Our certificate of incorporation includes a provision that, to the fullest extent permitted by the DGCL, eliminates the personal liability of our directors for monetary damages for breach of fiduciary duty as a director. In addition, together our certificate of incorporation and our bylaws require us to indemnify, to the fullest extent permitted by law, any person made or threatened to be made a party to an action or proceeding (whether criminal, civil, administrative or investigative) by reason of the fact that such person is or was a director, officer or employee of Sientra or any predecessor of ours, or serves or served at any other enterprise as a director, officer or employee at our request or the request of any predecessor of ours, against expenses (including attorneys’ fees), judgments, fines, settlements and other amounts actually and reasonably incurred in connection with any proceeding, arising by reason of the fact that such person is or was an agent of ours. Our bylaws also provide that we may, to the fullest extent provided by law, indemnify any person against expenses (including attorneys’ fees), judgments, fines, settlements and other amounts actually and reasonably incurred in connection with any proceeding, arising by reason of the fact that such person is or was an agent of ours. We are required to advance expenses incurred by our directors, officers, employees and agents in defending any action or proceeding for which indemnification is required or permitted, subject to certain limited exceptions. The indemnification rights conferred by our certificate of incorporation and bylaws are not exclusive.

In addition, we have entered into indemnification agreements with each of our executive officers and directors. We also maintain an officers and directors liability insurance policy.

The foregoing may reduce the likelihood of derivative litigation against our directors and executive officers and may discourage or deter stockholders or management from suing directors or executive officers for breaches of their duty of care, even though such actions, if successful, might otherwise benefit the company and our stockholders.

The underwriting agreement that we may enter into will provide for indemnification by any underwriters of the company, our directors, our officers who sign the registration statement and our controlling persons, if any, for some liabilities, including liabilities arising under the Securities Act.

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Item 16. Exhibits

Item 17. Undertakings

The undersigned registrant hereby undertakes:

1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement: (i) to include any prospectus required by Section 10(a)(3) of the Securities Act; (ii) to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the

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most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Securities and Exchange Commission (the “Commission”), pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and (iii) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

Provided, however, that paragraphs (a)(1)(i), (a)(1)(ii) and (a)(1)(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 (the “Exchange Act”), that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initialbona fide offering thereof.

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ii. Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

iii. The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of an undersigned registrant; and

iv. Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

6) That, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

7) To file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Commission under Section 305(b)(2) of the Trust Indenture Act.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on FormS-3 and has duly caused this registration statement to be signed on its behalf by the undersigned thereunto duly authorized in the City of Santa Barbara, State of California, on April 10, 2020.December 5, 2022.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose individual signature appears below hereby authorizes and appoints Ronald Menezes, Andrew C. Schmidt, and Oliver Bennett, and each of them, with full power of substitution and resubstitution and full power to act without the other, as his true and lawful attorney-in-fact and agent to act in his name, place and stead and to execute in the name and on behalf of each person, individually and in each capacity stated below, and to file any and all amendments (including post-effective amendments) to this Registration Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing, ratifying and confirming all that said attorneys-in-fact and agents or any of them or their or his substitute or substitutes may lawfully do or cause to be done by virtue thereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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