Material Event (Form 8-K)

Item 8.01 Other Events

Old Second Bancorp, Inc. (the "Company", "we," "us" and "our") will release financial results for the first quarter of 2026 after the market closes on April 22, 2026.

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We will also host an earnings call on Thursday, April 23, 2026 at 10:00 a.m. Eastern Time (9:00 a.m. Central Time). Investors may listen to our earnings call via a live webcast by accessing the link provided below, or alternatively, on the Events section of the Old Second Investor Relations website (https://investors.oldsecond.com/events). Investors are encouraged to register at the webcast link at least 10 minutes prior to the scheduled start of the call.

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Webcast URL: https://www.webcaster5.com/Webcast/Page/2239/53807

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A replay of the webcast will be available under the Events section of the Old Second Investor Relations website (https://investors.oldsecond.com/events) for up to one year after the earnings call date.

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