第一金融银行美股招股说明书(2025-10-29版)

To the Stockholders of BankFinancial Corporation On behalf of the board of directors of BankFinancial Corporation (“BankFinancial”), we are pleased to enclose the accompanyingproxy statement/prospectus relating to the proposed acquisition of BankFinancial by First Financial Bancorp. (“First Financial”). We arerequesting that you take certain actions as a holder of BankFinancial common stock (a “BankFinancial stockholder”). On August11, 2025, First Financial and BankFinancial entered into an Agreement and Plan of Merger (the “merger agreement”),pursuant to which First Financial will, upon the terms and subject to the conditions set forth in the merger agreement, acquireBankFinancial in an all-stock transaction. Under the merger agreement, BankFinancial will merge with and into First Financial, with First Financial as the survivingcorporation in the merger (the “merger”). Immediately following the merger, BankFinancial, National Association (“BankFinancialNA”),a national banking association and a wholly-owned subsidiary of BankFinancial, will merge with and into First Financial Bank, an Ohiostate-chartered bank and a wholly-owned subsidiary of First Financial, with First Financial Bank as the surviving bank (the “bankmerger”). At the effective time of the merger (the “effective time”), BankFinancial stockholders will receive 0.480 of a First Financial commonshare for each share of BankFinancial common stock they own. Based on the closing price of First Financial’s common shares on theNasdaq Global Select Market (“Nasdaq”), on August11, 2025, the last trading day before the public announcement of the merger, theexchange ratio represented approximately $11.34 in value for each share of BankFinancial common stock, representing mergerconsideration of approximately $141.3million on an aggregate basis. The value of the First Financial common shares at the time of the completion of the merger could be greater than, less than or thesame as the value of First Financial common shares on the date of the accompanying proxy statement/prospectus.We urge you to obtaincurrent market quotations of First Financial common shares (Nasdaq trading symbol “FFBC”) and BankFinancial common stock (Nasdaqtrading symbol “BFIN”). We expect the merger will qualify as a reorganization for U.S. federal income tax purposes. Accordingly, holders generally will notrecognize any gain or loss for U.S. federal income tax purposes on the exchange of shares of BankFinancial common stock for FirstFinancial common shares in the merger, except with respect to any cash received by BankFinancial stockholders in lieu of fractional FirstFinancial common shares. Based on the number of shares of BankFinancial common stock outstanding as of September 22, 2025, First Financial expects toissue approximately 5.98 million First Financial common shares to BankFinancial stockholders in the aggregate in the merger. Weestimate that First Financial shareholders will own approximately 94% and former BankFinancial stockholders will own approximately6% of the common shares of First Financial following the completion of the merger. BankFinancial will hold a special meeting of its stockholders in connection with the merger. At the special meeting, in addition toother business, BankFinancial will ask its stockholders to consider and vote upon the merger and the other transactions contemplated bythe merger agreement. Information about the special meeting and the merger is contained in this document. You are urged to read thisdocument carefully and in its entirety. The special meeting of BankFinancial stockholders will be held on December 18, 2025 at 11:00 a.m., Central Time at HiltonChicago/Oak Brook Hills Resort & Conference Center, 3500 Midwest Road, Oak Brook, Illinois60523. The BankFinancial board of directors unanimously recommends that stockholders vote “FOR” each of the proposals to be considered atthe special meeting. This proxy statement/prospectus provides you with detailed information about the merger agreement and the merger. It also contains orreferences information about First Financial and BankFinancial and certain related matters. You are encouraged to read this proxy statement/prospectus carefully. In particular, you should read the “Risk Factors” section beginning on page20for a discussion of the risks you shouldconsider in evaluating the proposed merger and how it will affect you. You can also obtain information about First Financial andBankFinancial from documents that have been filed with the Securities and Exchange Commission that are incorporated into this proxystatement/prospectus by reference. On behalf of the BankFinancial board of directors, thank you for your prompt attention to this important matter.Sincerely, By:/s/ F. Morgan Gasior F. Morgan GasiorChairman of the Board, President and ChiefExecutive Officer BankFinancial Corporation Neither the Securities and Exchange Commission nor any state securities commission has approved or