This prospectus relates to the resale or distribution from time to time by the selling securityholders of up to 25,493,02112,122,602 shares of Infrastructure and Energy Alternatives, Inc.’s (the “Company,” “IEA,” “we,” “us,” or “our”)the common stock, par value $0.0001 per share of the Company (the “Common Stock”) being offered by the. The selling stockholders identified herein, consisting of (i) 2,026,650 shares of issued and outstanding Common Stock, (ii) 1,631,471 shares of Common Stock issuable upon conversion of outstanding shares of Series A Preferred Stock, (iii) 7,672,067 shares of Common Stock issuable upon exercise of outstanding warrants (the “Warrants”), and (iv) 14,162,833 shares of Common Stock issuable upon conversion of outstanding shares of Series B Preferred Stock (the “Series B Preferred Stock”) issued to certain selling stockholders named herein. The Common Stock issuable upon conversion of the Series B Preferred Stock would only be issued upon a failure by the Company to mandatorily redeem the Series B Preferred Stock on February 15, 2025. The holders of the Series B Preferred Stock cannot cause a conversion earlier than such time or for any other reason than a failure on the part of the Company to mandatorily redeem the Series B Preferred Stock.

We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. We encourage you to read carefully this prospectus and any applicable prospectus supplement before you invest in our securities.Common Stock. We also encourage you to read the documents we have referred you to in the section entitled “Where You Can Find More Information” for additional information on us and our financial statements.

Our Common Stock is listed on The Nasdaq Capital Market, or NASDAQ, under the symbol “IEA.” On April 6,November 5, 2021, the closing saleslast reported sale price of our Common Stock as reported on The Nasdaq Capital Market, was $14.62$11.76 per share.

This prospectus is part of a resale registration statement that we filed with the Securities and Exchange CommissionSEC using a “shelf” registration process. The selling stockholderssecurityholders may offer anduse the shelf registration statement to sell from timeup to time, an aggregate of up to 25,493,02112,122,602 shares of our Common Stock under this prospectus. from time to time through any means described in the section entitled “Plan of Distribution.”

In some cases, we andor the selling stockholderssecurityholders will also be required to provide a prospectus supplement containing specific information about the selling stockholderssecurityholders and the terms on which they are offering and selling our Common Stock. We may also provide a prospectus supplement to add to, update or change the information contained in this prospectus. You should read this prospectus and any accompanying prospectus supplement, and any documents incorporated by reference, as well as any post-effective amendments to the registration statement of which this prospectus is a part, before you make any investment decision. To the extent there is a conflict between the information contained in this prospectus and any applicable prospectus supplement, including the information incorporated by reference, you should rely on the information in the applicable prospectus supplement.

Neither we nor the selling stockholderssecurityholders have authorized anyone to provide you with information different from that contained in this prospectus or any accompanying prospectus supplement, including the information incorporated by reference herein. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

Neither we nor the selling stockholderssecurityholders have done anything that would permit the use of or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about and comply with any restrictions relating to the offering of the Common Stock and the distribution of this prospectus outside the United States.

The selling stockholderssecurityholders may only offer to sell, and seek offers to buy, ourthe Common Stock registered hereby in jurisdictions where offers and sales areof such Common Stock is permitted. The information contained in this prospectus speaks only as of the date of this prospectus.

This prospectus and the documents incorporated by reference herein contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The forward-looking statements can be identified by the use of forward-looking terminology including “may,” “should,” “likely,” “will,” “believe,” “expect,” “anticipate,” “estimate,” “forecast,” “seek,” “target,” “continue,” “plan,” “intend,” “project,” or other similar words. Other than statements of historical fact included in this prospectus and the documents incorporated by reference herein, all statements regarding expectations for future transactions, financial performance, business strategies, expectations for our business, future operations, financial position, estimated revenues and losses, projected costs, prospects, plans, objectives and beliefs of management are forward-looking statements.

These forward-looking statements are based on information available as of the date hereof and as of the respective dates of the documents containing the forward-looking statements, and our management’s current expectations, forecasts and assumptions, and involve a number of judgments, risks and uncertainties. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give any assurance that such expectations will prove correct. Forward-looking statements should not be relied upon as representing our views as of any subsequent date. As a result of a number of known and unknown risks and uncertainties, our actual results or performance may be materially different from those expressed or implied by these forward-looking statements. Some factors that could cause actual results to differ include:

We do not undertake any obligation to update forward-looking statements to reflect events or circumstances after the date they were made, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws.

The following table providestables provide the names of the selling stockholders,securityholders, information known to us regarding their beneficial ownership of our Common Stock by the selling stockholders as of March 31,November 8, 2021, and the number of shares of our Common Stock offered by the selling stockholderssecurityholders in this offering, and the number of shares of our Common Stock and the percentage of our Common Stock to be beneficially owned by the selling stockholderssecurityholders after completion of this offering. Information with respect to beneficial ownership is based on our records, information filed with the SEC or information furnished to us by the selling stockholders.securityholders.

Beneficial ownership is determined according to the rules of the SEC and generally means that a person has beneficial ownership of a security if he, she, or it possesses sole or shared voting or investment power of that security, including securities underlying warrants and options that are currently exercisable or exercisable within 60 days of March 31,November 8, 2021. In calculating percentage ownership for the selling stockholders,securityholders, we treated as outstanding securities underlying warrants and options that are currently exercisable or exercisable within 60 days of March 31,November 8, 2021.

The aggregate percentage of shares of Common Stock reported as owned by each of the selling stockholderssecurityholders listed below is based on 22,905,03147,974,783 shares of Common Stock outstanding as of March 19,November 8, 2021.

We and certain of the selling stockholderssecurityholders and certain other parties are parties to that certain Amended and Restated Registration Rights Agreement, dated March 26, 2018 (as amended, modified and otherwise supplemented (the “Registration Rights Agreement”)), which provides the selling stockholderssecurityholders and other parties thereto with customary demand and piggyback registration rights, and the registration statement of which this prospectus supplement and the accompanying prospectus form a part was filed in connection therewith. The Common Stock offered by this prospectus are the subject of a shelf offering notice issued by the selling stockholders pursuant to the Registration Rights Agreement.

Certain of our significant stockholders are permitted to exercise their registration rights under the Registration Rights Agreement to have us file a registration statement in respect of the resale of the shares of Common Stock (and securities convertible into Common Stock) beneficially owned by such significant stockholders, and the underwriters shall permit us to cooperate and comply with such exercise of registration rights as required under the Registration Rights Agreement.

John Paul Roehm, our President, Chief Executive Officer and a director; Chris Hanson, our Executive Vice President of Wind Operations; Brian Hummer, our Executive Vice President of Operations, and Terence Montgomery and Derek Glanvill, directors, are members of Infrastructure and Energy Alternatives, LLC.

Mr. Roehm and his spouse are trustees and beneficiaries of the Roehm Living Trust. As noted above, Mr. Roehm is our President, Chief Executive Officer and is a member of our board of directors.

David. E. Bostwick was the Company’s General Counsel until January 2019, and was employed in the Company’s legal department thereafter until his resignation in April 2019.

Herman White II is currently employed by the Company and was the founder of the Company’s predecessor. Additionally, Mr. White is a stockholder of HB White Investments, Inc. and may be deemed a beneficial owner of the securities registered in the name of HB White Investments, Inc. pursuant to this Registration Statement.registration statement.

The Trustee of the ADL Revocable Trust is Andrew D. Layman who was out Chief Financial Officer from 2015 until February 2020, when as previously disclosed, Mr. Layman resigned from the Company. The beneficiaries of the ADL Revocable Trust are Mr. Layman, his spouse and their children.

We are registering Common Stock offered by this prospectus on behalf of the selling stockholders.securityholders. The selling stockholders,securityholders, which as used herein includes donees, pledgees, transferees or other successors-in-interest selling Common Stock received after the date of this prospectus from a selling stockholdersecurityholder as a gift, pledge, limited liability company or partnership distribution or other transfer, may, from time to time, sell, transfer, distribute or otherwise dispose of any or all of their securities on Nasdaq or any other stock exchange, market or trading facility on which such securities are traded or in private transactions. These dispositions may be at fixed prices, at prevailing market prices at the time of sale, at prices related to the prevailing market price, at varying prices determined at the time of sale or at negotiated prices.

The selling stockholderssecurityholders may use any one or more of the following methods when disposing of their securities or interests therein:

The selling stockholderssecurityholders may, from time to time, pledge or grant a security interest in some or all of the securities owned by them and, if they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell their securities, from time to time, under this prospectus, or under an amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act amending the list of selling stockholderssecurityholders to include the pledgee, transferee or other successors in interest as selling stockholderssecurityholders under this prospectus. The selling stockholderssecurityholders also may transfer their securities in

In connection with the sale of our securities or interests therein, the selling stockholderssecurityholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of our securities in the course of hedging the positions they assume. The selling stockholderssecurityholders may also sell their securities short and deliver these securities to close out their short positions, or loan or pledge such securities to broker-dealers that in turn may sell these securities. The selling stockholders

securityholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealers or other financial institutions of securities offered by this prospectus, which securities such broker-dealers or other financial institutions may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The aggregate proceeds to the selling stockholderssecurityholders from the sale of the securities offered by them will be the purchase price of the security less discounts or commissions, if any. Each of the selling stockholderssecurityholders reserves the right to accept and, together with their agents from time to time, to reject, in whole or in part, any proposed purchase of their securities to be made directly or through agents. We will not receive any of the proceeds from the resale of securities being offered by the selling stockholderssecurityholders named herein. However, we will receive proceeds from the exercise of the WarrantsPre-Funded Warrant if they are exercised by a holder thereof.

The selling stockholderssecurityholders also may resell all or a portion of their securities in open market transactions in reliance upon Rule 144 under the Securities Act, provided that they meet the criteria and conform to the requirements of that rule.

Underwriters, broker-dealers and agents that act in connection with the sale of securities might be deemed to be “underwriters” within the meaning of Section 2(a)(11) of the Securities Act, and any commissions received by them and any profit on the resale of the securities sold by them while acting as principals might be deemed to be underwriting discounts or commissions under the Securities Act.

A selling stockholdersecurityholder that is an entity may elect to make a pro rata in-kind distribution of the Common Stock to its members, partners or stockholders pursuant to the registration statement of which this prospectus is a part by delivering a prospectus with a plan of distribution. Such members, partners or stockholders would thereby receive freely tradeable Common Stock pursuant to the distribution through a registration statement. To the extent a distributee is an affiliate of ours (or to the extent otherwise required by law), we may file a prospectus supplement in order to permit the distributees to use the prospectus to resell the Common Stock acquired in the distribution. A selling stockholdersecurityholder that is an individual may make gifts of Common Stock covered hereby. Such donees may use the prospectus to resell the ordinary shares or, if required by law, we may file a prospectus supplement naming such donees.

To the extent required, the securities to be sold, the names of the selling stockholders,securityholders, the respective purchase prices and public offering prices, the names of any agent, dealer or underwriter, and any applicable commissions or discounts with respect to a particular offer will be set forth in an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement that includes this prospectus.

In order to comply with the securities laws of some states, if applicable, our securities may be sold in these jurisdictions only through registered or licensed brokers or dealers. In addition, in some states our securities may not be sold unless they have been registered or qualified for sale or an exemption from registration or qualification requirements is available and is complied with.

If a selling stockholdersecurityholder wants to sell its securities under this prospectus in the United States, the selling stockholdersecurityholder will also need to comply with state securities laws, also known as “Blue Sky laws,” with regard to secondary sales. All states offer a variety of exemptions from registration for secondary sales. Many states, for example, have an exemption for secondary trading of securities registered under Section 12(g) of the Securities Exchange Act, or for securities of issuers that publish continuous disclosure of financial and non-financial information in a recognized securities manual, such as Standard & Poor’s. The broker for a selling stockholdersecurityholder will be able to advise a selling stockholdersecurityholder in which states our securities are exempt from registration with that state for secondary sales.

Any person who purchases our securities from a selling stockholdersecurityholder offered by this prospectus who then wants to sell such securities will also have to comply with Blue Sky laws regarding secondary sales.

When the registration statement that includes this prospectus becomes effective, and a selling stockholdersecurityholder indicates in which state(s) such selling stockholdersecurityholder desires to sell such selling stockholder’ssecurityholder’s securities, we will be able to identify whether such selling stockholdersecurityholder will need to register or will be able to rely on an exemption therefrom.

We have advised the selling stockholderssecurityholders that the anti-manipulation rules of Regulation M under the Exchange Act may apply to sales of securities in the market and to the activities of the selling stockholderssecurityholders and their affiliates. In addition, we will make copies of this prospectus (as it may be supplemented or amended from time to time) available to the selling stockholderssecurityholders for the purpose of satisfying the prospectus delivery requirements of the Securities Act. The selling stockholderssecurityholders may indemnify any

We have agreed to indemnify the selling stockholderssecurityholders against liabilities, including certain liabilities under the Securities Act and state securities laws, relating to the registration of the securities offered by this prospectus.

We are required to pay all of our fees and expenses incident to the registration of the securities covered by this prospectus, including with regard to compliance with state securities or “blue sky” laws. The registration expenses of any registration effected by preparing and filing a registration statement or similar document in compliance with the requirements of the Securities Act, and the applicable rules and regulations promulgated thereunder, and such registration statement becoming effective, will be borne by the Company. The parties to the Registration Rights Agreement shall be responsible for any underwriters’ commissions and discounts or brokerage fees in respect of the registrable securities sold by them and the fees and expenses of any legal counsel representing them except as otherwise set forth in the Registration Rights Agreement.

The validity of the securities offered by this prospectus will be passed upon for us by Jones Walker LLP, New Orleans, Louisiana.

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus incorporates by reference the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (in each case, other than those filings, documents or the portions of those documents not deemed to be filed, including any information furnished pursuant to Items 2.02 or 7.01 of a Current Report on Form 8-K) (i) after the date of the initial registration statement and prior to effectiveness of the registration statement, and (ii) after the effectiveness of the registration statement until the offering of the securities under the registration statement is terminated or completed:

You mayWe will provide to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request and without charge, a copy of these filings, at no cost,the documents referred to above that we have incorporated in this prospectus supplement by reference. You can request such copies by writing or telephoning us at the following address or telephone number:

SetThe following table sets forth below are theall expenses to be incurredpayable by us in connection with this registration. All the issuance and distribution ofamounts shown are estimates except for the securities to be registered. The amounts set forth below are estimates.SEC registration fee:

Our Certificate of Incorporation provides that all of our directors, officers, employees and agents will be entitled to be indemnified by us to the fullest extent permitted by Section 145 of the Delaware General Corporation Law (the “DGCL”), as is currently in effect or as may be amended. Section 145 of the DGCL as currently in effectamended, provides that a corporation may indemnify directors and officers as well as other employees and individuals against expenses, including attorneys’ fees, judgments, fines and amounts paid in settlement in connection with specified actions, suits and proceedings whether civil, criminal, administrative, or investigative, other than a derivative action by or in the right of the corporation, if they acted in good faith and in a manner they reasonably believed to be in or not opposed to the best interests of the corporation and, with respect to any criminal action or proceeding, had no reasonable cause to believe their conduct was unlawful. A similar standard is applicable in the case of derivative actions, except that indemnification extends only to expenses, including attorneys’ fees, incurred in connection with the defense or settlement of such action and the statute requires court approval before there can be any indemnification where the person seeking indemnification has been found liable to the corporation. The statute provides that it is not exclusive of other indemnification that may be granted by a corporation'scorporation’s certificate of incorporation, Bylaws, disinterested director vote, stockholder vote, agreement or otherwise.

OurThe Certificate of Incorporation of Infrastructure and Energy Alternatives, Inc. provides that all of its directors, officers, employees and agents will be entitled to be indemnified to the fullest extent permitted by Section 145 of the DGCL.

The Certificate of Incorporation of Infrastructure and Energy Alternatives, Inc. provides that expenses (including attorneys’ fees) incurred by an officer or director in defending any civil, criminal, administrative, or investigative action, suit or proceeding for which such officer or director may be entitled to indemnification thereunder shall be paid by the Companycorporation in advance of the final disposition of such action, suit or proceeding upon receipt of an undertaking by or on behalf of such director or officer to repay such amount if it shall ultimately be determined that he or she is not entitled to be indemnified by the Companycorporation as authorized thereby.

The CompanyInfrastructure and Energy Alternatives, Inc. has obtained directors'directors’ and officers’ insurance to cover its directors, officers and some of its other employees for certain liabilities.

OurThe Bylaws of Infrastructure and Energy Alternatives, Inc. provide for the indemnification of ourits directors, officers or other persons in accordance with our Certificate of Incorporation.

We haveInfrastructure and Energy Alternatives, Inc. has entered into agreements with ourits officers and directors to provide contractual indemnification in addition to the indemnification provided for in ourits current Certificate of Incorporation. The indemnification agreements require us,it, among other things, to indemnify ourits directors and officers against certain liabilities that may arise by reason of their status or service as directors and officers and to advance their expenses incurred as a result of any proceeding against them as to which they could be indemnified.

The general effect of the foregoing is to provide indemnification to officers and directors for liabilities that may arise by reason of their status as officers or directors, other than liabilities arising from willful or intentional misconduct, acts or omissions not in good faith, unlawful distributions of corporate assets or transactions from which the officer or director derived an improper personal benefit.

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that isit has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Indianapolis, State of Indiana, on April 7,November 8, 2021.

KNOW ALL PERSONS BY THESE PRESENTS, that theeach person whose signature appears below hereby constitutes and appoints John Paul Roehm, Peter J. Moerbeek and Gil Melman,Erin Roth, or either one of them (with full power in each to act alone), as his or her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him or her and in his or her name, place, and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement, and to sign any registration statement for the same offering covered by the registration statement that is to be effective upon filing pursuant to Rule 462(b) promulgated under the Securities Act of 1933 and to file the same, with all exhibits thereto, and other documents in connection therewith, with the U.S. 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 requisite and necessary to be done in connection therewith and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby 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 hereof.