Filed by Fifth Third Bancorp

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934

Subject Company: MB Financial, Inc.

SEC File No.: 001-36599

Filer’s SEC File No.: 001-33653

Date: October 23, 2018

Fifth Third Announces Third Quarter 2018 Results

Diluted earnings per share of $0.61

Reported results included a negative $0.03 from certain items on page 2

CEO Commentary

“Our strong quarterly results again reflected the progress we have made toward achieving our long-term financial targets. Our balance sheet continued to become more resilient, as evidenced by the consistent improvement in key credit quality metrics. Although market dynamics remained challenging during the quarter, our net interest margin increased and we generated solid loan, deposit, and household growth. We continued to diligently manage expenses as we drive toward achieving our long-term efficiency target.”

“Five months after we initially announced our planned acquisition of MB Financial, we remain confident in our ability to achieve the expected financial synergies from the transaction. We have received the necessary shareholder approvals for the acquisition and have recently re-submitted our pro-forma capital plans. We continue to expect the transaction to close in the first quarter of 2019.”

“With improving returns and a strengthened balance sheet, we remain very confident in our ability to achieve our long-term financial targets under Project NorthStar and remain well-positioned to outperform through the cycle.”

-Greg D. Carmichael, Chairman, President and CEO

Fifth Third Bancorp (Nasdaq: FITB) today reported third quarter 2018 net income of $433 million compared to net income of $1.0 billion in the year-ago quarter. Net income available to common shareholders was $418 million, or $0.61 per diluted share, compared to $999 million, or $1.35 per diluted share in the year-ago quarter. Prior quarter net income was $586 million and net income available to common shareholders was $563 million, or $0.80 per diluted share.

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Compared to the year-ago quarter, NII increased $70 million, or 7 percent, reflecting higher short-term market rates and growth in interest-earning assets, partially offset by an increase in funding costs. NIM increased 16 bps, primarily driven by higher short-term market rates.

Compared to the prior quarter, NII increased $23 million, or 2 percent, reflecting higher short-term market rates and a higher day count. NIM increased 2 bps, primarily driven by higher short-term market rates, loan growth, and an increase in higher-yielding consumer loans, partially offset by a higher day count.

Reported noninterest income decreased $998 million, or 64 percent, from the year-ago quarter, and decreased $180 million, or 24 percent, from the prior quarter. The comparisons reflect the impact of certain significant items in the table on page 4.

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Compared to the year-ago quarter, corporate banking revenue decreased $1 million, or 1 percent, as a decline in loan syndication and equity capital markets revenue was partially offset by higher financial risk management fees. Mortgage banking net revenue decreased $14 million, or 22 percent, primarily driven by lower origination fees and gains on loan sales. Mortgage originations of $1.9 billion decreased 12 percent. Wealth and asset management revenue increased $12 million, or 12 percent, primarily driven by higher personal asset management revenue and brokerage fees. Card and processing revenue increased $3 million, or 4 percent, due to higher credit card spend volume and higher debit transaction volume, partially offset by higher rewards.

Compared to the prior quarter, corporate banking revenue decreased $20 million, or 17 percent, primarily driven by decreases in loan syndication revenue and corporate bond fees. Mortgage banking net revenue decreased $4 million, or 8 percent, primarily driven by lower origination fees and gains on loan sales as well as elevated negative net valuation adjustments. Mortgage originations decreased 12 percent. Wealth and asset management revenue increased $6 million, or 6 percent, primarily driven by higher personal asset management revenue and brokerage fees. Card and processing revenue decreased $2 million, or 2 percent, reflecting higher rewards.

Compared to the year-ago quarter, noninterest income excluding the items in the table above increased $15 million, or 3 percent. Compared to the prior quarter, noninterest income excluding these items increased $19 million, or 3 percent.

Other noninterest income on a reported basis in the current and previous quarters was impacted by the items disclosed in the table above with the exception of all securities losses / (gains). Excluding these items, other noninterest income of $103 million increased $17 million, or 20 percent compared to the year-ago quarter. Compared to the prior quarter, other noninterest income excluding these items increased $34 million, or 49 percent. Performance compared to the year-ago and prior quarter reflected higher private equity investment income.

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Compared to the year-ago quarter, noninterest expense increased $33 million, or 3 percent, primarily driven by higher compensation related expense as well as technology and communication expense.

Compared to the prior quarter, noninterest expense decreased $29 million, or 3 percent. Excluding both a $19 million compensation expense, primarily related to a staffing review, and a $10 million contribution to the Fifth Third Foundation from the prior quarter, noninterest expense was flat. Performance primarily reflected lower compensation expense partially offset by higher technology and communications expense, as well as increased marketing expense.

Compared to the year-ago quarter, average portfolio loans and leases increased 1 percent, primarily driven by higher commercial and industrial (C&I) and other consumer loans, partially offset by declines in home equity loans, commercial leases, and automobile loans. Period end portfolio loans and leases increased 2 percent. Compared to the prior quarter, average portfolio loans and leases increased 1 percent, primarily driven by higher other consumer and C&I loans, partially offset by a decline in home equity loans. Period end portfolio loans and leases increased 2 percent.

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Compared to the year-ago quarter, average commercial portfolio loans and leases increased 2 percent, primarily driven by higher C&I loans led by growth in corporate banking and middle market lending. Compared to the prior quarter, average commercial portfolio loans and leases increased 1 percent, primarily driven by growth in C&I and commercial real estate loans. Period end commercial line utilization was 35 percent, stable compared to both the year-ago and prior quarter.

Compared to the year-ago quarter, average consumer portfolio loans increased 1 percent, primarily driven by higher other consumer loans, partially offset by declines in home equity and automobile loans. Compared to the prior quarter, average consumer portfolio loans increased 1 percent, primarily driven by higher other consumer loans, partially offset by a decline in home equity.

Average securities and other short-term investments were $34.8 billion compared to $33.8 billion in the year-ago quarter, and $34.9 billion in the prior quarter. Average available-for-sale debt and other securities of $32.6 billion were up 4 percent compared to the year-ago quarter, and flat compared to the prior quarter.

Compared to the year-ago quarter, both average transaction and core deposits increased 3 percent. Performance was primarily driven by higher commercial interest checking deposits and consumer money market deposits, partially offset by lower commercial demand deposits. Commercial transaction deposits increased 2 percent and consumer transaction deposits increased 3 percent.

Compared to the prior quarter, both average transaction and core deposits were flat. Performance continued to reflect migration from demand deposits to interest-bearing accounts. Commercial transaction deposits increased 1 percent, and consumer transaction deposits decreased 1 percent.

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Compared to the year-ago quarter, average wholesale funding decreased 4 percent, as strong deposit growth outpaced growth in interest-earning assets. Compared to the prior quarter, average wholesale funding increased 1 percent. Performance reflected higher federal funds borrowings, partially offset by a decline in other short-term borrowings.

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Compared to the year-ago quarter, NPLs decreased $103 million, or 20 percent, with the resulting NPL ratio of 0.43 percent decreasing 12 bps. Repossessed personal property decreased $2 million and OREO balances decreased $2 million. NPAs decreased $107 million, or 19 percent, with the resulting NPA ratio of 0.48 percent, decreasing 12 bps.

Compared to the prior quarter, NPLs decreased $34 million, or 8 percent, with the resulting NPL ratio decreasing 4 bps. Repossessed personal property increased $1 million and OREO balances increased $1 million. NPAs decreased $32 million, or 7 percent, with the resulting NPA ratio decreasing 4 bps.

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The provision for loan and lease losses totaled $86 million in the current quarter compared to $67 million in the year-ago quarter and $33 million in the prior quarter. The resulting allowance for loan and lease loss ratio represented 1.17 percent of total portfolio loans and leases outstanding in the current quarter, compared with 1.31 percent in the year-ago quarter and 1.17 in the prior quarter. The allowance for loan and lease losses represented 270 percent of nonperforming loans and leases, and 243 percent of nonperforming assets in the current quarter.

Net losses charged-off totaled $72 million in the current quarter compared to $68 million in the year-ago quarter and $94 million in the prior quarter. The resulting NCO ratio of 0.30 percent in the current quarter increased 1 bp compared to the year-ago quarter and decreased 11 bps compared to the prior quarter.

Capital ratios remained strong during the quarter. The CET1 ratio was 10.67 percent, the tangible common equity to tangible assets ratio was 9.12 percent (excluding unrealized gains/losses), and 8.63 percent (including unrealized gains/losses). The Tier I risk-based capital ratio was 11.78 percent, the Total risk-based capital ratio was 15.01 percent, and the Tier I leverage ratio was 10.10 percent.

During the third quarter of 2018, Fifth Third entered into open market repurchase transactions of 16.9 million shares, or approximately $500 million, of its outstanding common stock, which settled between July 24, 2018 and August 6, 2018.

Tax Rate

The effective tax rate was 15.6 percent compared with 31.9 percent in the year-ago quarter and 15.5 percent in the prior quarter.

Other

Fifth Third has re-submitted its CCAR 2018 capital plan to the Federal Reserve, recognizing the pro forma impact of the combined Fifth Third MB Financial post-merger entity. In the meantime, Fifth Third expects to resume capital distribution activities consistent with the originally-submitted April 2018 capital plan. The timing and amount of this activity is subject to market conditions and applicable securities laws.

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On September 18, 2018, MB Financial, Inc. common stockholders approved Fifth Third’s acquisition originally announced May 21, 2018. The acquisition is expected to close in the first quarter of 2019, subject to regulatory approvals and other customary closing conditions.

As of September 30, 2018, Fifth Third Bank owned approximately 10.3 million units representing a 3.3 percent interest in Worldpay Holding, LLC, convertible into shares of Worldpay, Inc., a publicly traded firm. Based upon Worldpay’s closing price of $101.27 on September 30, 2018, Fifth Third’s interest in Worldpay was valued at approximately $1.04 billion. The difference between the market value and the book value of Fifth Third’s interest in Worldpay’s shares is not recognized in Fifth Third’s equity or capital.

Conference Call

Fifth Third will host a conference call to discuss these financial results at 9:00 a.m. (Eastern Time) today. This conference call will be webcast live and may be accessed through the Fifth Third Investor Relations website at www.53.com (click on “About Us” then “Investor Relations”).

Those unable to listen to the live webcast may access a webcast replay through the Fifth Third Investor Relations website at the same web address. Additionally, a telephone replay of the conference call will be available after the conference call until approximately November 6, 2018 by dialing 800-585-8367 for domestic access or 404-537-3406 for international access (passcode 4083528#).

Corporate Profile

Fifth Third Bancorp is a diversified financial services company headquartered in Cincinnati, Ohio. As of September 30, 2018, the Company had $142 billion in assets and operates 1,152 full-service Banking Centers, and 2,443 Fifth Third branded ATMs in Ohio, Kentucky, Indiana, Michigan, Illinois, Florida, Tennessee, West Virginia, Georgia and North Carolina. In total, Fifth Third provides its customers with access to approximately 53,000 fee-free ATMs across the United States. Fifth Third operates four main businesses: Commercial Banking, Branch Banking, Consumer Lending, and Wealth & Asset Management. As of September 30, 2018, Fifth Third also had a 3.3% interest in Worldpay Holding, LLC, a subsidiary of Worldpay, Inc. Fifth Third is among the largest money managers in the Midwest and, as of September 30, 2018, had $376 billion in assets under care, of which it managed $38 billion for individuals, corporations and not-for-profit organizations through its Trust and Registered Investment Advisory businesses. Investor information and press releases can be viewed at www.53.com. Fifth Third’s common stock is traded on the NASDAQ^® Global Select Market under the symbol “FITB.”

Earnings Release End Notes

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IMPORTANT ADDITIONAL INFORMATION AND WHERE TO FIND IT

In connection with the proposed merger, Fifth Third Bancorp has filed with the SEC a Registration Statement on Form S-4 that includes the Proxy Statement of MB Financial, Inc. and a Prospectus of Fifth Third Bancorp, as well as other relevant documents concerning the proposed transaction. This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. INVESTORS AND STOCKHOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND THE PROXY STATEMENT/PROSPECTUS REGARDING THE MERGER AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION.

A free copy of the Proxy Statement/Prospectus, as well as other filings containing information about Fifth Third Bancorp and MB Financial, Inc., may be obtained at the SEC’s Internet site (http://www.sec.gov). You will also be able to obtain these documents, free of charge, from Fifth Third Bancorp at ir.53.com or from MB Financial, Inc. by accessing MB Financial, Inc.’s website at investor.mbfinancial.com.

Copies of the Proxy Statement/Prospectus can also be obtained, free of charge, by directing a request to Fifth Third Investor Relations at Fifth Third Investor Relations, MD 1090QC, 38 Fountain Square Plaza, Cincinnati, OH 45263, by calling (866) 670-0468, or by sending an e-mail to ir@53.com or to MB Financial, Attention: Corporate Secretary, at 6111 North River Road, Rosemont, Illinois 60018, by calling (847) 653-1992 or by sending an e-mail to dkoros@mbfinancial.com.

Fifth Third Bancorp and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the stockholders of MB Financial, Inc. in respect of the transaction described in the Proxy Statement/Prospectus. Information regarding Fifth Third Bancorp’s directors and executive officers is contained in Fifth Third Bancorp’s Annual Report on Form 10-K for the year ended December 31, 2017 and its Proxy Statement on Schedule 14A, dated March 6, 2018, which are filed with the SEC. Information regarding MB Financial, Inc.’s directors and executive officers is contained in its Proxy Statement on Schedule 14A filed with the SEC on April 3, 2018. Additional information regarding the interests of those participants and other persons who may be deemed participants in the transaction may be obtained by reading the Proxy Statement/Prospectus regarding the proposed merger. Free copies of this document may be obtained as described in the preceding paragraph.

FORWARD-LOOKING STATEMENTS

This communication contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 including, but not limited to, Fifth Third Bancorp’s and MB Financial, Inc.’s expectations or predictions of future financial or business performance or conditions. Forward-looking statements are typically identified by words such as “believe,” “expect,” “anticipate,” “intend,” “target,” “estimate,” “continue,” “positions,” “plan,” “predict,” “project,” “forecast,” “guidance,” “goal,” “objective,” “prospects,” “possible” or “potential,” by future conditional verbs such as “assume,” “will,” “would,” “should,” “could” or “may”, or by variations of such words or by similar expressions. These forward-looking statements are subject to numerous assumptions, risks and uncertainties, which change over time. Forward-looking statements speak only as of the date they are made and we assume no duty to update forward-looking statements. Actual results may differ materially from current projections.

In addition to factors previously disclosed in Fifth Third Bancorp’s and MB Financial, Inc.’s reports filed with or furnished to the SEC and those identified elsewhere in this communication, the following factors, among others, could cause actual results to differ materially from forward-looking statements or historical performance: the ability to obtain regulatory approvals and meet other closing conditions to the merger, including approval of the merger by MB Financial, Inc.’s stockholders on the expected terms and schedule, including the risk that regulatory approvals required for the merger are not obtained or are obtained subject to conditions that are not anticipated; delay in closing the merger; difficulties and delays in integrating the businesses of MB Financial, Inc. or fully realizing cost savings and other benefits; business disruption following the merger; changes in asset quality and credit risk; the inability to sustain revenue and earnings growth; changes in interest rates and capital markets; inflation; customer acceptance of Fifth Third Bancorp’s products and services; customer borrowing, repayment, investment and deposit practices; customer disintermediation; the introduction, withdrawal, success and timing of business initiatives; competitive conditions; the inability to realize cost savings or revenues or to implement integration plans and other consequences associated with mergers, acquisitions and divestitures; economic conditions; and the impact, extent and timing of technological changes, capital management activities, and other actions of the Federal Reserve Board and legislative and regulatory actions and reforms.

Annualized, pro forma, projected and estimated numbers are used for illustrative purpose only, are not forecasts and may not reflect actual results.

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Quarterly Financial Review for September 30, 2018

Table of Contents

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