Exhibit 8.2

812 SAN ANTONIO STREET SUITE 600 AUSTIN, TEXAS 78701   TEL  512 • 583 • 5900 FAX   512 • 583 • 5940

June 22, 2018

Post Oak Bancshares, Inc.

2000 West Loop South, Suite 100

Houston, Texas 77027

Attention: Roland Williams, Chairman, President and Chief Executive Officer

Ladies and Gentlemen:

We have acted as special counsel to Post Oak Bancshares, Inc., a Texas corporation and registered bank holding company under the Bank Holding Company Act of 1956, as amended (“Post Oak”), in connection with the proposed merger (the “Merger”) of Post Oak with and into Allegiance Bancshares, Inc., a Texas corporation and registered bank holding company under the Bank Holding Company Act of 1956 (“Allegiance”), pursuant to that certain Agreement and Plan of Merger, dated April 30, 2018, by and between Allegiance and Post Oak (the “Agreement”). Capitalized terms used but not defined herein shall have the meanings ascribed to them in the Agreement. At your request, we are rendering our opinion concerning certain United States federal income tax matters relating to the Merger in connection with the filing of the registration statement on Form S-4 (as may be amended from time to time, and including the proxy statement/prospectus contained therein, the “Registration Statement”) with the U.S. Securities and Exchange Commission (“Commission”).

In providing our opinion, we have examined and relied upon the Agreement, the proxy statement/prospectus and other information included as part of Registration Statement, the representation letters of Allegiance and Post Oak delivered to us for purposes of rendering our opinion stated herein (the “Representation Letters”) and such other documents as we have deemed necessary or appropriate for purposes of our opinion. In addition, we have assumed that (i) the transaction will be consummated in accordance with the provisions of the Agreement and as described in the Registration Statement (and no transaction or condition described therein and affecting this opinion will be waived by any party), (ii) the statements concerning the transaction and the parties thereto set forth in the Agreement are true, complete and correct, and the Registration Statement is true, complete and correct, (iii) the factual statements and representations made by Allegiance and Post Oak in their respective Representation Letters are true, complete and correct as of the date hereof and will remain true, complete and correct at all times up to and including the Effective Time, (iv) any such statements and representations made in the Representation Letters “to the knowledge of” any person or similarly qualified are and will be true, complete and correct without such qualification, and (v) Allegiance, Post Oak and their respective subsidiaries will treat the Merger for United States federal income tax purposes in a manner consistent with the opinion set forth below. If any of the above-described assumptions are untrue for any reason or if the transaction is consummated in a manner that is different from the manner described in the Agreement or the Registration Statement, our opinion as expressed below may be adversely affected.

www.fkhpartners.com

Post Oak Bancshares, Inc.

June 22, 2018

Page 2

Based upon the foregoing and subject to the assumptions, qualifications and limitations stated herein and set forth in the Registration Statement, we are of the opinion that, under currently applicable United States federal income tax law, (i) the Merger, when consummated in accordance with the terms of the Agreement and the Registration Statement, will qualify as a “reorganization” within the meaning of Section 368(a) of the Code; and (ii) the descriptions of law and the legal conclusions contained in the proxy statement/prospectus included in the Registration Statement under the heading “Material U.S. Federal Income Tax Consequences of the Merger” are correct in all material respects, and the discussion thereunder represents an accurate summary of the United States income tax consequences of the Merger that are material to the U.S. shareholders of Post Oak and Allegiance.

Other than the opinion set forth above, we express no opinion on any issue relating to (i) the tax consequences of the transactions contemplated by the Agreement, (ii) the appropriate method to determine fair market value of any stock or other consideration received in any sale or exchange, and (iii) the laws of any jurisdiction other than the federal laws of the United States of America. Our opinion relates solely to material United States federal income tax consequences of the Merger, and no opinion is implied or should be inferred beyond those matters. Our opinion is based on current provisions of the Code, Treasury Regulations promulgated thereunder, published pronouncements of the Internal Revenue Service and case law, any of which may be changed at any time with retroactive effect. Any change in applicable laws or the facts and circumstances surrounding the transaction, or any inaccuracy in the statements, facts, assumptions or representations upon which we have relied, may affect the continuing validity of our opinion as set forth herein. We assume no responsibility to inform Post Oak of any such change or inaccuracy that may occur or come to our attention.

Although we may have acted as counsel to Post Oak in connection with certain matters other than the Merger, our engagement is limited to certain matters about which we have been consulted. Consequently, there may exist matters of a factual or legal nature involving Post Oak as to which we have not been consulted and have not represented Post Oak. This opinion letter is limited to the matters stated herein and no opinions may be implied or inferred beyond the matters expressly stated herein. This opinion letter is delivered solely for the benefit of Post Oak and its shareholders that exchange their shares of Post Oak common stock for shares of Allegiance common stock in connection with the Merger, and no other party or entity is entitled to rely hereon without the express prior written consent of this firm.

We hereby consent to the filing of this opinion with the Commission as Exhibit 8.2 to the Registration Statement and to the references to our firm and this opinion contained in the Registration Statement. In giving such consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations promulgated by the Commission thereunder.

Very truly yours,

/s/ Fenimore, Kay, Harrison & Ford, LLP