Exhibit 23.3

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in this Amendment No.1 to the Registration Statement (No. 333-194050) on Form S-4 of First Interstate BancSystem, Inc. of our reports dated February 28, 2014, relating to our audits of the consolidated financial statements and internal control over financial reporting, which appear in the Annual Report on Form 10-K of First Interstate BancSystem, Inc. for the year ended December 31, 2013.

We also consent to the reference to our firm under the caption “Experts” in the Prospectus, which is part of this Registration Statement.

/s/ McGladrey LLP

Des Moines, Iowa

April 2, 2014