PROXY STATEMENT

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INVESTAR HOLDING CORPORATION

PROXY STATEMENT

ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD ON WEDNESDAY, MAY 18, 2016

We are furnishing this proxy statement to the shareholders of Investar Holding Corporation in connection with the solicitation of proxies by its board of directors for use at the Annual Meeting of Shareholders of Investar Holding Corporation to be held at 3:00 p.m., Central time, on Wednesday, May 18, 2016, at Investar Bank, 10500 Coursey Boulevard, Third Floor, Baton Rouge, Louisiana 70816, as well as in connection with any adjournments or postponements of the meeting. In this proxy statement, Investar Holding Corporation is referred to as “Investar”, “we”, “our”, “us” or the “Company”, and Investar Bank is referred to as the “Bank”.

As required by the Securities and Exchange Commission, or SEC, rules, we are making this proxy statement, our proxy card and our Annual Report on Form 10-K for the year ended December 31, 2015 (which serves as our annual report to shareholders) available to our shareholders electronically. On April 18, 2016, we posted these materials on our Internet website, http://www.proxydocs.com/ISTR. On the same date, we mailed this proxy statement, our proxy card and Annual Report on Form 10-K for the year ended December 31, 2015 to our shareholders.

QUESTIONS AND ANSWERS ABOUT THE ANNUAL MEETING, VOTING YOUR SHARES

AND THE PROXY MATERIALS

Who is soliciting proxies from the shareholders?

Our board of directors, on behalf of the Company, is soliciting your proxy. The proxy provides you with the opportunity to vote on the proposals presented at the annual meeting, whether or not you attend the meeting.

What will be voted on at the annual meeting?

Your proxy will also give the proxy holders discretionary authority to vote the shares represented by the proxy on any matter, other than the above proposals, that is properly presented for action at the annual meeting.

How will we solicit proxies, and who bears the cost of proxy solicitation?

Our directors, officers and employees may solicit proxies by telephone, mail, facsimile, via the Internet or by overnight delivery service. These individuals do not receive separate compensation for these services. Also, we have retained and pay a fee to Computershare, Inc. to perform services in connection with our common stock, including assistance with the solicitation of proxies, but we pay no separate compensation to Computershare, Inc. solely for the solicitation of proxies. Finally, in accordance with SEC regulations, we will reimburse brokerage firms and other persons representing beneficial owners of our common stock for their reasonable expenses in forwarding solicitation materials to such beneficial owners.

Who can vote at the annual meeting?

Our board of directors has fixed the close of business on Monday, March 21, 2016, as the record date for our annual meeting. Only shareholders of record on that date are entitled to receive notice of and vote at the annual

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meeting. As of March 21, 2016, our only outstanding class of securities was common stock, $1.00 par value per share. On that date, we had 40,000,000 shares of common stock authorized, of which 7,296,553 shares were outstanding.

If you, rather than your broker, are the record holder of our stock, you can vote either in person at the annual meeting or by proxy, whether or not you attend the annual meeting. If you would like to attend the annual meeting in person and need directions, please contact Patrice Theriot by email at patrice.theriot@investarbank.com or by telephone at (225) 448-5468. You may vote your shares by proxy via a toll-free telephone number, on the Internet or by signing, dating and mailing the accompanying proxy card in the envelope provided. Instructions regarding the three methods of voting by proxy are contained on the proxy card.

How many votes must be present to hold the annual meeting?

A “quorum” must be present to hold our annual meeting. The presence, in person or by proxy, of a majority of the votes entitled to be cast at the annual meeting constitutes a quorum. Your shares, once represented for any purpose at the annual meeting, are deemed present for purposes of determining a quorum for the remainder of the meeting and for any adjournment, unless a new record date is set for the adjourned meeting. This is true even if you abstain from voting with respect to any matter brought before the annual meeting.

How many votes does a shareholder have per share?

Our shareholders are entitled to one vote for each share held.

What is the required vote on each proposal?

Directors are elected by plurality vote; the candidates up for election who receive the highest number of votes cast, up to the number of directors to be elected, are elected. Shareholders do not have the right to cumulate their votes.

The proposal to ratify our appointment of Postlethwaite & Netterville APAC, or Postlethwaite & Netterville, as our independent registered public accountants for 2016 is approved by our shareholders if the votes cast favoring the ratification exceed the votes cast opposing the ratification.

How will the proxy be voted, and how are votes counted?

If your shares are registered directly in your name, you are the shareholder of record of those shares and the annual report and proxy statement have been mailed to you by us. If you vote by proxy (either by properly completing and returning a paper proxy card or voting by telephone or on the Internet), the shares represented by your proxy will be voted at the annual meeting as you instruct, including any adjournments or postponements of the meeting. If you return a signed proxy card but do not provide any voting instructions on the proxy card, your shares will be voted at the annual meeting and any adjournments or postponements in accordance with the recommendations of the board as follows:

If your shares are held in a stock brokerage account by a bank, broker or other nominee, you are considered the beneficial owner of shares held in street name and these proxy materials are being forwarded to you by your bank, broker or other nominee that is considered the shareholder of record of those shares. As the beneficial owner, you have the right to direct your bank, broker or other nominee holding your shares in street name on how

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to vote your shares and must provide voting instructions to your bank, broker or other nominee, or your shares will not be voted on any proposal on which your bank, broker or the other party does not have discretionary authority to vote. The New York Stock Exchange (“NYSE”) rules determine which proposals presented at annual meetings of shareholders are “routine” or “non-routine.” If a proposal is determined to be routine, your bank, broker or other nominee has discretionary authority and may vote your shares on the proposal without receiving voting instructions from you. If a proposal is determined to be non-routine, your bank, broker, or other nominee does not have discretionary authority and may not vote your shares on the proposal without receiving your voting instructions. The ratification of our appointment of our independent registered public accountants is generally considered a routine matter for broker voting purposes, but the election of directors is not considered a routine matter.

A “broker non-vote” occurs when a bank, broker or other party holding shares for which you are a beneficial owner returns a valid proxy, but does not vote on a particular proposal because it does not have discretionary authority to vote on the matter and has not received voting instructions from the shareholder for whom it is holding shares. Broker non-votes will be treated as shares present for the purpose of determining whether a quorum is present at the meeting, but they will not be considered present for purposes of calculating the vote on a particular matter, nor will they be counted as a vote “for” or “against” a matter or as an abstention on the matter.

An abstention from voting by a shareholder who is either present in person at the annual meeting or represented by proxy will be treated as not being “cast” for purposes of such vote and will be counted neither “for” nor “against” the matter subject to the abstention. Abstentions will not affect the outcome of the vote on matters that must be approved by the holders of a majority of the votes cast or by plurality vote.

Can a proxy be revoked?

Yes. You can revoke or change your proxy at any time before it is used to vote your shares by (1) giving written notice to our Corporate Secretary before the annual meeting, (2) timely delivering to us another proxy with a later date or (3) appearing in person and voting at the annual meeting if you, rather than your broker, are the record holder of our stock. Your attendance alone at the annual meeting will not be enough to revoke your proxy. Written notice of the revocation of a proxy should be delivered to the following address: Randolf F. Kassmeier, Corporate Secretary, Investar Holding Corporation, 7244 Perkins Road, Baton Rouge, Louisiana 70808.

How do I obtain a separate set of proxy materials or request a single set for my household?

We have adopted a procedure approved by the SEC called “householding.” Under this procedure, which will apply to future annual meetings, we will deliver only one copy of our annual report and proxy statement to shareholders who have the same address and last name unless one or more of these shareholders notifies us that they wish to continue receiving individual copies. This procedure reduces our printing costs and postage fees. Although only one copy of our annual report and proxy statement will be delivered to each address, each shareholder sharing that address will continue to be able to access or receive a separate proxy card for his or her individual voting instructions.

If shareholders sharing an address wish to receive a separate annual report and a separate proxy statement in the future, please contact Randolf F. Kassmeier, our Corporate Secretary, at (504) 609-2105, or write to Mr. Kassmeier at Investar Holding Corporation, Attn.: Corporate Secretary, 7244 Perkins Road, Baton Rouge, Louisiana 70808. You may also send an email to Mr. Kassmeier at randy.kassmeier@investarbank.com. If you have multiple accounts in your name or share an address with other shareholders and receive multiple copies of our annual report and proxy statement, you can authorize us to discontinue mailing multiple copies by calling or writing to or emailing our Corporate Secretary as instructed above.

Shareholders who beneficially own shares of our common stock held in street name may contact their brokerage firm, bank, broker-dealer or other similar organization to request information about householding.

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STOCK OWNERSHIP OF CERTAIN BENEFICIAL OWNERS

As of March 21, 2016, we had approximately 789 shareholders of record. The following table sets forth information regarding the beneficial ownership of our common stock as of March 21, 2016 by each person or entity, including any group (as that term is used in Section 13(d)(3) of the Securities Exchange Act of 1934, as amended, or the Exchange Act), known to us to be the beneficial owner of 5% or more of our outstanding common stock. Beneficial ownership has been determined in accordance with Rule 13d-3 under the Exchange Act and is based upon the number of shares of our common stock outstanding as of March 21, 2016, which was 7,296,553 shares.

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STOCK OWNERSHIP OF DIRECTORS AND OFFICERS

The following table includes information about the common stock owned by our directors, nominees and executive officers, as of March 21, 2016, including their name, position and the number of shares beneficially owned by each. Each of the persons listed in the table below under the heading “Directors and Nominees” currently serves as a director of the Company. Unless otherwise noted, the persons below have sole voting power and investment power with respect to the listed shares (subject to any applicable community property laws). The business address for each of the directors and executive officers listed below is 7244 Perkins Road, Baton Rouge, Louisiana 70808. In computing each listed person’s particular percentage ownership, we deemed as outstanding any shares of common stock subject to options or warrants held by that person that are exercisable currently or within 60 days of March 21, 2016. However in accordance with SEC rules, we did not deem these shares outstanding for the purpose of computing the percentage ownership of any other person.

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SECTION 16(A) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

Section 16(a) of the Exchange Act requires our executive officers and directors and persons who own more than 10% of a registered class of our equity securities to file with the SEC and the Nasdaq reports of ownership of our securities and changes in their ownership on Forms 3, 4 and 5. Executive officers, directors and greater than 10% shareholders are required by SEC rules to furnish us with copies of all Section 16(a) reports they file.

Based solely upon a review of the reports on Forms 3 and 4 and amendments thereto furnished to us in 2015 and Forms 5 and amendments thereto furnished to us with respect to 2015, or written representations from reporting persons that no Form 5 filing was required, we believe that in 2015, all of our executive officers, directors and greater than 10% owners timely filed all reports they were required to file under Section 16(a) with the exception of Mr. Nelson, who inadvertently failed to timely file two Forms 4 to report purchases of common stock, and Mr. Lukinovich, who inadvertently failed to timely file two Forms 4 to report purchases of common stock by his children and also filed an amendment to his original Form 3 to correct errors in holdings reported in his Form 3 and to reflect indirect holdings omitted from the Form 3. All of these transactions were subsequently reported on Forms 4.

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BOARD OF DIRECTORS

Board Composition

Our board is currently comprised of 13 directors, all of whom have been nominated for reelection at the annual meeting for a one-year term. Mr. John Emmett “J.E.” Brignac, Jr. resigned from his position on the board in February 2016. We thank him for his service to the Company.

Information about Director Nominees

The following lists each director currently serving on our board and includes a brief discussion of the experience, qualifications and skills that led us to conclude that such individual should serve as a member of our board. We believe that our board of directors consists of a diverse collection of individuals who possess the integrity, education, work ethic and ability to work with others necessary to oversee our business effectively and to represent the interests of all shareholders. The information presented below highlights certain notable experience, qualifications and skills for each director, but does not provide an exhaustive catalog of each and every qualification and skill that a director possesses.

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CORPORATE GOVERNANCE

Board Independence

Our board has determined that each of James M. Baker, James H. Boyce, III, Robert M. Boyce, Sr., Robert L. Freeman, David J. Lukinovich, Suzanne O. Middleton, Andrew C. Nelson, M.D., Carl R. Schneider, Jr. and Frank L. Walker is an “independent director” as defined under Rule 5605(a)(2) of the Nasdaq Marketplace Rules. Mr. John Emmett “J.E.” Brignac, who resigned from the board in February 2016, was also an “independent director.”

The board considered the relationships between our directors and Investar or the Bank when determining each director’s status as an “independent director” under Rule 5605(a)(2) of the Nasdaq Marketplace Rules, including the relationships listed below under “CERTAIN TRANSACTIONS.” Other than the relationships listed below under “CERTAIN TRANSACTIONS,” the board determined that these relationships did not affect any director’s status as an “independent director.” Furthermore, we are not aware of any family relationships between any director, executive officer or person nominated to become a director or executive officer.

Board Leadership Structure

The board has not adopted a formal policy regarding the separation of the roles of Chairman of the Board and Chief Executive Officer because the board believes that it is in our best interests to make that determination from time to time based on the position and direction of our organization and the composition of our board. Currently, Mr. Hidalgo serves as Chairman of the Board of the Company and the Bank, while Mr. D’Angelo is the President and Chief Executive Officer of the Company and the Bank. We believe at this time this structure (as opposed to combining the positions of Chairman of the Board and Chief Executive Officer) is appropriate for us for two primary reasons. First, having a separate board chairman allows Mr. D’Angelo to focus fully on his primary responsibilities, which include implementing our strategic plans and managing the day-to-day operations of the Company and the Bank, rather than being occupied with fulfilling the duties of the Chairman of the Board, such as scheduling board meetings and otherwise managing the board of directors. Second, we believe that having the board chairman position separate from the Chief Executive Officer allows the board of directors to more effectively fulfill its obligation to oversee our management.

Board’s Role in Risk Oversight

Although the full board of directors is ultimately responsible for the oversight of our risk management processes, the board is assisted in this task by a number of its committees and committees of the Bank’s board of directors. These committees are primarily responsible for considering and overseeing the risks within their particular area of concern. For example, our audit committee focuses on financial reporting and operational risk. As provided in its charter, the audit committee is required to meet regularly with management, our independent registered public accountants and our internal auditors to discuss the integrity of our financial reporting processes and internal controls as well as the steps that have been taken to monitor and control risks related to such matters. The Bank’s credit committee is primarily responsible for credit and other risks arising in connection with our lending activities, which includes overseeing management committees that also address these risks. The Bank’s asset-liability committee monitors our interest rate risk, with the goal of structuring our asset-liability composition to maximize net interest income while minimizing the adverse impact of changes in interest rates on net interest income and capital. Finally, our compensation committee, whose duties are described in more detail below, evaluates the risks that our executive compensation programs may generate.

Each committee meets regularly with management to assist it in identifying all of the risks within such committee’s areas of responsibility and in monitoring and, where necessary, taking appropriate action to mitigate the applicable risks. Following each committee meeting, the committee chairman provides a report at the next board meeting to the full board of directors on issues related to such committee’s risk oversight duties. To the extent that any risks reported to the full board need to be discussed outside the presence of management, the board will call an executive session to discuss these issues.

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We believe the board’s approach to fulfilling its risk oversight responsibilities complements its leadership structure. In his capacity as Chairman of the Board, Mr. Hidalgo reviews whether board committees are addressing their risk oversight duties in a comprehensive and timely manner. Based on the outcome of these reviews, Mr. D’Angelo can assist these committees in fulfilling their duties by (1) requiring that our management team provide these committees with all requested reports and other information as well as with access to our employees and (2) implementing recommendations of the various board committees to mitigate risk.

Board Meeting Attendance

Our board held 12 meetings during 2015. During 2015, all of our directors attended at least 75% of the total number of board meetings and the meetings of the committees on which they served during the periods that they served. The members of the board who are “independent directors” under Nasdaq Rule 5605(a)(2) met in executive session twice during 2015.

All of our current directors attended the 2015 annual meeting. Although we do not have a policy requiring director attendance at our annual meeting, we expect our entire board to attend this year’s annual meeting.

Board Committees

To assist in the performance of its responsibilities, our board of directors has established standing committees. These committees include our executive committee as well as our audit committee, compensation committee and nominating and governance committee. The board also may establish additional committees as it deems necessary or appropriate, in accordance with applicable law and regulations and our corporate governance documents. The table below reflects the current membership of our standing committees.

Executive Committee

The executive committee has been empowered to make decisions with respect to matters under the direction and control of our board when the board is not in session. The executive committee held two meetings during 2015.

Audit Committee

The board has determined that each member of the audit committee (1) is an “independent director” as defined in Rule 5605(a)(2) of the Nasdaq Marketplace Rules, (2) meets the criteria for independence in Rule 10A-3(b)(1) of the Exchange Act and (3) satisfies the other requirements for audit committee membership under

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the Nasdaq Marketplace Rules. The board has determined that David J. Lukinovich qualifies as an “audit committee financial expert” under applicable SEC rules and regulations and satisfies the financial sophistication requirements under Rule 5605(c)(2)(A) of the Nasdaq Marketplace Rules. During 2015, the audit committee held seven meetings.

The audit committee assists the board of directors in fulfilling its responsibilities for general oversight of our financial reporting process. Among other things, the committee’s responsibilities include:

The audit committee has adopted a written charter, a copy of which is available at www.investarbank.com by clicking on “Corporate Governance” under the “Investor Relations” tab and then clicking on “Audit Committee Charter”.

Compensation Committee

The board has determined that each member of the compensation committee (1) is an “independent director” as defined in Rule 5605(a)(2) of the Nasdaq Marketplace Rules and (2) is a “non-employee director,” as defined in Rule 16b-3 promulgated under the Exchange Act. In determining that each member of the compensation committee is an independent director, the board considered factors specifically relevant to determining whether such member has or had a relationship with us or the Bank that materially affects the member’s ability to be independent from management in connection with the duties of a compensation committee member, including those factors listed in Rule 5605(d)(2) of the Nasdaq Marketplace Rules. The compensation committee meets with the frequency necessary to perform its duties and responsibilities. The committee met a total of four times during 2015.

The compensation committee is responsible for overseeing our compensation arrangements for our executives and directors. Among other things, the compensation committee reviews and approves our overall compensation structure, policies and programs (including benefit plans) to ensure that our compensation structure appropriately incentivizes our executive officers and other employees and otherwise meets our corporate objectives. The compensation committee is also responsible for setting the compensation payable to our Chief Executive Officer and our other named executive officers and for administering our equity incentive plans and other incentive compensation plans. Except as may be limited by applicable law, stock exchange rules and its charter, the compensation committee may delegate its authority to the extent it deems necessary or appropriate. Responsibility for the ministerial or day-to-day administration of our executive compensation program has been delegated to officers of the Bank. Please refer to the “Executive Compensation” and “Compensation Tables” sections below for more information our executive compensation arrangements and the compensation paid in 2015.

The compensation committee has adopted a written charter that sets forth its rights and responsibilities that is available at www.investarbank.com by selecting “Corporate Governance” under the “Investor Relations” tab and then selecting “Compensation Committee Charter.”

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Nominating and Governance Committee

The board has determined that each member of the nominating committee is an “independent director” as defined in Rule 5605(a)(2) of the Nasdaq Marketplace Rules. During 2015, the nominating committee held one meeting.

The nominating and governance committee oversees the process for selecting and recommending to the board persons for election as directors and administers our corporate governance policies. The committee is composed solely of members who satisfy the applicable independence requirements of the SEC and the Nasdaq Stock Market for nominating and governance committees.

When evaluating director candidates, the committee’s objective is to craft a board composed of individuals with a broad mix of backgrounds and experiences and possessing, as a whole, all of the skills and expertise necessary to guide a company like us in the prevailing business environment. The committee uses the same criteria to assess all candidates for director, regardless of who proposed the candidate. Section 2.13 of our By-laws lists the minimum qualifications that any director or director candidate must possess, which include, as to such individual, the following: (1) ownership (together with his or her affiliates) of at least $100,000 of our stock, unless the board determines otherwise; (2) satisfaction of all qualifications to serve as a director under applicable laws, rules and regulations; (3) no felony convictions or conduct inconsistent with our code of ethics or otherwise not in the best interests of us or our employees; and (4) attendance (or ability to attend) at least 80% of all board and committee meetings.

In addition to the minimum qualifications in our By-laws, the nominating and governance committee considers whether the candidate possesses the following qualifications and qualities:

Although the board has not adopted a formal policy regarding the consideration of diversity when evaluating director candidates, the board believes that its membership should reflect diversity in its broadest sense. Accordingly, whenever the nominating and governance committee evaluates a potential candidate, we expect it to consider a candidate’s gender, ethnicity, experience, education, geographic location and difference of viewpoint, in the context of the composition of the board as a whole.

The nominating and governance committee has adopted a written charter that sets forth its rights and responsibilities that is available at www.investarbank.com by selecting “Corporate Governance” under the “Investor Relations” tab and then selecting “Nominating and Governance Committee Charter.”

Usually, nominees for election to the board are proposed by the current members of the board. The nominating and governance committee will also consider candidates that shareholders and others recommend. Shareholder recommendations should be addressed to: Randolf F. Kassmeier, Corporate Secretary, Investar Holding Corporation, 7244 Perkins Road, Baton Rouge, Louisiana 70808. Your recommendations must be submitted to us no earlier than January 18, 2017, and no later than February 17, 2017, for consideration as a possible nominee for election to the board at our 2017 annual meeting.

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The specific requirements of our advance notice and eligibility provisions, which apply to shareholder recommendations of candidates for director, are set forth in Article Eight of our By-laws, a copy of which is available upon request. Among other things, a shareholders’ notice must include the following information as to each nominee:

The shareholders’ notice must also set forth the name and address of the nominating shareholder and information relating to, among other things (1) all direct and indirect ownership interests (including hedges, short positions and derivatives) and economic interests in our stock (such as rights to dividends or fees related to an increase or decrease in the value of our stock) and all proxies and other arrangements to vote our stock held by the nominating shareholder, and (2) all other information that the shareholder would be required to disclose under Section 14 of the Exchange Act and the rules and regulations thereunder in connection with the solicitation of proxies by such shareholder in a contested election. If a shareholder intends to recommend a nominee for election as director on behalf of the beneficial owner of the shares that the recommending shareholder is the record owner of, the recommending shareholder must also provide the information described above with respect to the beneficial owner.

C ommunications with the Board

Shareholders can send communications to the board by contacting Randolf F. Kassmeier, our Corporate Secretary, in one of the following ways:

If you request information or ask questions that can more efficiently be addressed by management, Mr. Kassmeier will respond to your questions instead of the board. He will forward to the audit committee any communications concerning employee fraud or accounting matters and will forward to the full board any communications relating to corporate governance or those requiring action by the board of directors.

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