Exhibit 23.1
Consent of Independent Registered Public Accounting Firm
We consent to the reference to our firm under the caption Experts in the Registration Statement
(Form S-3) and the related Prospectus of First Financial Bancorp for the registration of senior
debt securities, subordinated debt securities, junior subordinated debt securities, common shares,
purchase contracts, units, warrants, rights, trust preferred capital
securities and guarantees, and to the incorporation by reference
therein of our reports dated February 26, 2008, with respect to the consolidated financial
statements of First Financial Bancorp, and the effectiveness of internal control over financial
reporting of First Financial Bancorp, included in its Annual Report (Form 10-K) for the year ended
December 31, 2007, filed with the Securities and Exchange Commission.
/s/
Ernst & Young LLP
Cincinnati, Ohio
September 29, 2008