UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT PURSUANT

TO SECTION 13 OR 15(D) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (date of earliest event reported):  February 22, 2018

MainSource Financial Group, Inc.

(Exact name of registrant as specified in its charter)

2105 North State Road 3 Bypass

Greensburg, Indiana 47240

(Address of principal executive offices)

(812) 663-0157

(Registrant’s Telephone Number,

Including Area Code)

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below):

o                                    Written communications pursuant to Rule 425 under the Securities Act (17 CFR 240.425)

o                                    Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o                                    Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o                                    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).                Emerging growth company o

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 8.01  Other Events.

On February 22, 2018, the Company and First Financial Bancorp. (“First Financial”) issued a joint press release announcing the receipt of regulatory approval from the Board of Governors of the Federal Reserve System and the Ohio Division of Financial Institutions for the proposed merger of the Company with and into First Financial.  The joint press release, which also announces the closing date of the proposed merger, is attached to this Current Report on Form 8-K as Exhibit 99.1 and is incorporated herein by reference.

Forward-Looking Statements

Certain statements contained in this release which are not statements of historical fact constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995.  Such statements include, but are not limited to, certain plans, expectations, goals, projections and benefits relating to the proposed merger (the “Merger”) between MainSource Financial Group (“MainSource”) and First Financial Bancorp (“First Financial”), which are subject to numerous assumptions, risks and uncertainties.  Words such as “believes,” “anticipates,” “likely,” “expected,” “estimated,” “intends” and other similar expressions are intended to identify forward-looking statements but are not the exclusive means of identifying such statements.  Please refer to each of  MainSource’s and First Financial’s Annual Report on Form 10-K for the year ended December 31, 2016, as well as their other filings with the SEC, for a more detailed discussion of risks, uncertainties and factors that could cause actual results to differ from those discussed in the forward-looking statements.

Forward-looking statements are not historical facts but instead express only management’s beliefs regarding future results or events, many of which, by their nature, are inherently uncertain and outside of the management’s control.  It is possible that actual results and outcomes may differ, possibly materially, from the anticipated results or outcomes indicated in these forward-looking statements.  In addition to factors previously disclosed in reports filed by  MainSource and First Financial with the SEC, risks and uncertainties for  MainSource, First Financial and the combined company include, but are not limited to:  the possibility that any of the anticipated benefits of the proposed Merger will not be realized or will not be realized within the expected time period; the risk that integration of  MainSource’s operations with those of First Financial will be materially delayed or will be more costly or difficult than expected; the inability to close the Merger in a timely manner; diversion of management’s attention from ongoing business operations and opportunities; the failure to satisfy other conditions to completion of the Merger, including receipt of required regulatory and other approvals; the failure of the proposed Merger to close for any other reason; the challenges of integrating and retaining key employees; the effect of the announcement of the Merger on  MainSource’s, First Financial’s or the combined company’s respective customer relationships and operating results; the possibility that the Merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events; and general competitive, economic, political and market conditions and fluctuations.  All forward-looking statements included in this filing are made as of the date hereof and are based on information available at the time of the filing.  Except as

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required by law, neither MainSource nor First Financial assumes any obligation to update any forward-looking statement.

Item 9.01.                                      Financial Statements and Exhibits.

(d)                               Exhibits.

99.1                        Joint Press Release issued by MainSource Financial Group, Inc. and First Financial Bancorp. on February 22, 2018.

*         *         *

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EXHIBIT INDEX

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date:  February 22, 2018

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