Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statements on Form S-8 (Nos. 333-199692 and 333-201880) and on Form S-3 (No. 333-215238) of Investar Holding Corporation and any related prospectus of our report dated March 9, 2017 relating to our audit of the consolidated financial statements of Investar Holding Corporation and the effectiveness of internal control over financial reporting of Investar Holding Corporation included in this Annual Report (Form 10-K) for the year ended December 31, 2016.

/s/ Postlethwaite & Netterville, APAC

Baton Rouge, Louisiana

March 9, 2017