mofginvestorpresentation

• • • • • • • • • • • • • 4

• • 8

• • • • • • • • • • 12

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 13

• 14

• 15

• • 16

• Complementary Iowa expansion into the Dubuque and Des Moines markets, as well as entry into Southwest Wisconsin, creating an approximately $4.7 billion asset institution Strategic • Unique opportunity to achieve immediate scale in Dubuque market (#2 deposit market share) Rationale • Adds $1.1 billion of trust assets under administration to MidWestOne Financial Group, Inc.’s (“MOFG”) current trust business • Meaningful estimated EPS accretion of greater than 15% in 2020(1) and 2021(1) Compelling Financial • TBV dilution earn-back period estimated to be < 3.0 years Returns • Estimated IRR well above MOFG’s cost of equity capital • Increased size and scale with identified and achievable efficiencies • Comprehensive due diligence process on ATBancorp’s business, loan portfolio, and non-interest Low Risk income lines of business • ATBancorp’s loan portfolio is high quality with expected reduced credit risk • MOFG management team is experienced in integrating acquisitions (1) Assumes cost saves are fully phased-in 18

ATBancorp Headquarters: Dubuque, IA Number of Branches: 17 Total Assets ($mm): $1,388 Gross Loans ($mm): $1,167 Total Deposits ($mm) $1,078 Note: Financial data as of April 30, 2019 Company Overview • ATBancorp was formed in 1985 to serve as a holding company for American Trust & Savings Bank of Dubuque Iowa (established in 1911) • ATBancorp was a two-bank holding company, also serving as the holding company for its Wisconsin subsidiary, American Bank & Trust MOFG (45) nd ATBancorp (17) • Strong local reputation showcased by 2 ranked deposit market share(1) in Dubuque, IA MSA (1) Deposit market share data as of 6/30/18 19