• Old Second Bancorp recently reported that its net interest income has grown 24.4% annually over the past five years, supported by a high-yielding loan book and a 4.8% net interest margin.
• This combination of consistent net interest income expansion and a best-in-class margin suggests the bank has been capturing market share in its core markets.
• Next, we’ll explore how Old Second’s strong net interest income growth could reshape its existing investment narrative and long-term appeal.

Find companies with promising cash flow potential yet trading below their fair value.

Old Second Bancorp Investment Narrative Recap

To own Old Second Bancorp, you need to be comfortable with a focused, Illinois-centered bank that is trying to convert a strong net interest margin into durable earnings, despite exposure to local economic cycles and credit risks. The latest data on 24.4% annual net interest income growth and a 4.8% margin supports the key near term catalyst of revenue expansion, but does not materially change the biggest risk, which remains the health of its concentrated Midwest footprint.

The recent Q3 2025 earnings release is especially relevant here, with net interest income of US$82.78 million up from US$60.58 million a year earlier, underscoring how Old Second’s high yielding loan book is feeding through to the income line. At the same time, lower net income and EPS over the period highlight that credit costs, operating expenses, or integration items can still offset the benefit of stronger margin economics, which matters for how investors think about the sustainability of the story.

Yet beneath Old Second’s impressive margin profile, investors should be aware of its concentrated exposure to Illinois and the local economy...

Old Second Bancorp's narrative projects $357.7 million revenue and $141.3 million earnings by 2028. This requires 8.2% yearly revenue growth and a $57.6 million earnings increase from $83.7 million today.

Uncover how Old Second Bancorp's forecasts yield a $22.92 fair value, a 13% upside to its current price.

Exploring Other Perspectives

Two Simply Wall St Community fair value estimates span a relatively tight US$19.55 to US$22.92 range, underscoring how even a small group of investors can see things differently. When you weigh this against Old Second’s reliance on Illinois economic health, it underlines why understanding both local credit conditions and your own assumptions about risk is essential before forming a view on the bank’s long term performance.

Explore 2 other fair value estimates on Old Second Bancorp - why the stock might be worth as much as 13% more than the current price!

Build Your Own Old Second Bancorp Narrative

Disagree with existing narratives? Create your own in under 3 minutes - extraordinary investment returns rarely come from following the herd.

• A great starting point for your Old Second Bancorp research is our analysis highlighting 2 key rewards and 2 important warning signs that could impact your investment decision.
• Our free Old Second Bancorp research report provides a comprehensive fundamental analysis summarized in a single visual - the Snowflake - making it easy to evaluate Old Second Bancorp's overall financial health at a glance.

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This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.