EX-5.1

Exhibit 5.1




October 18, 2019 First Financial Bankshares, Inc. 400 Pine Street Abilene, Texas 79601		Norton Rose Fulbright US LLP 2200 Ross Avenue, Suite 3600 Dallas, Texas 75201-7932 United States Tel +1 214 855 8000 Fax +1 214 855 8200 nortonrosefulbright.com

Ladies and Gentlemen:

We have acted as special counsel to First Financial Bankshares, Inc., a Texas corporation (the “Company”), in connection with the Registration Statement on Form S-4 (the “Registration Statement”), to be filed with the Securities and Exchange Commission (the “SEC”) under the Securities Act of 1933, as amended (the “Securities Act”), on the date hereof, relating to the registration of shares (the “Shares”) of the Company’s common stock, par value $0.01 per share. The Shares are proposed to be offered to the shareholders of TB&T Bancshares, Inc., a Texas corporation (“TB&T”) pursuant to the Agreement and Plan of Reorganization, dated as of September 19, 2019 (the “Reorganization Agreement”), by and among the Company, Brazos Merger Sub, Inc., and TB&T. This opinion letter is delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

In rendering the opinion expressed herein, we have examined originals, or copies certified to our satisfaction, of such records, agreements, instruments and documents as we have deemed necessary as a basis for the opinion hereinafter expressed. In all such examinations we have assumed the genuineness of all signatures, the authenticity of all documents, certificates and records submitted to us as originals, the conformity to original documents, certificates and records of all documents, certificates and records submitted to us as copies, and the truthfulness of all statements of fact contained therein. We also have assumed, with respect to all parties to agreements or instruments relevant hereto, other than the Company, that such parties had the requisite power and authority (corporate or other) to execute, deliver and perform such agreements or instruments, that such agreements or instruments have been duly authorized by all requisite action (corporate or otherwise), that such agreements or instruments have been executed and delivered by such parties and that such agreements and instruments are the valid, binding and enforceable obligations of such parties. As to various matters of fact relevant to the opinion hereinafter expressed, we have relied upon, and have assumed the accuracy of, certificates and oral or written statements and other information of or from public officials, officers and representatives of the Company and others.

For purposes of this opinion, we have assumed that, prior to the issuance of any Shares, (i) the Registration Statement, including all amendments, will have become effective under the Securities Act and (ii) the Shares will have been issued and delivered pursuant to the Reorganization Agreement.

Based on the foregoing, and subject to the limitations, assumptions and qualifications set forth herein, we are of the opinion that the Shares will be validly issued, fully paid and non-assessable.

Norton Rose Fulbright US LLP is a limited liability partnership registered under the laws of Texas.

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