Exhibit 23

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the following Registration Statements of FirstMerit Corporation and subsidiaries (“FirstMerit”) of our reports dated February 28, 2013, with respect to the consolidated financial statements of FirstMerit and the effectiveness of internal control over financial reporting of FirstMerit, included in this Annual Report (Form 10-K) for the year ended December 31, 2012:

Form S-8 No. 33-47074

Form S-8 No. 33-47147

Form S-8 No. 33-57557

Form S-8 No. 33-63101

Form S-8 No. 333-66129

Form S-8 No. 333-72287

Form S-8 No. 333-78953

Form S-8 No. 333-120446

Form S-8 No. 333-138624

Form S-8 No. 333-156217

Form S-8 No. 333-173628

Form S-8 No. 333-175894

Form S-3 No. 333-185132

Form S-4 No. 333-185121

/s/ Ernst & Young LLP

Akron, Ohio

February 28, 2013