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

Exhibit 23.1

Consent of Rehmann Robson, P.C.

CONSENT OF INDEPENDENT REGISTERED
PUBLIC ACCOUNTING FIRM

Board of Directors
Isabella Bank Corporation
Mt. Pleasant, MI

We consent to the incorporation by reference in the Registration Statement on Form S-3 pertaining to the Isabella Bank Corporation Stockholder Dividend Reinvestment and Employee Stock Purchase Plan of our integrated audit report dated February 29, 2008 relating to the consolidated financial statements and the effectiveness of internal control over financial reporting which appears on page 34 of Form 10-K for the year ended December 31, 2007. We also consent to the reference to our Firm under the caption “Experts” in such Registration Statement.

/s/ REHMANN ROBSON, P.C.

Saginaw, Michigan
June 2, 2008

Exhibit 23.1 — 1