Isabella Bank (ISBA) S-3D Registration of securities, dividend or interest reinvestment plans, immediately effective

EXHIBIT 23.1

Consent of Rehmann Robson LLC

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the reference to us under the caption “Experts” in this Registration Statement on Form S-3 pertaining to the Stockholder Dividend Reinvestment and Employee Stock Purchase Plan, and to the incorporation by reference therein of our integrated audit report dated March 16, 2020, relating to the consolidated financial statements and the effectiveness of internal control over financial reporting of Isabella Bank Corporation, included in its Annual Report on Form 10-K for the year ended December 31, 2019.

                                            /s/ Rehmann Robson LLC

Saginaw, Michigan

November 4, 2020