OLD SECOND BANCORP INC — Director's Dealing 2026

Feb 24, 2026

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: OLD SECOND BANCORP INC (OSBC)
CIK: 0000357173
Period of Report: 2026-02-17

Reporting Person: ADAMS BRADLEY S. (N/A)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2026-02-17	Restricted Stock Units	A	25428	—	Acquired	102872	Direct
2026-02-21	Restricted Stock Units	F	2923	$20.57	Disposed	93926	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Old Second Bancorp, Inc. Common Stock	149331	Direct
Old Second Bancorp, Inc. Common Stock	10124	Indirect

Footnotes

F1: Each restricted stock unit represents a contingent right to receive one share of common stock. The reporting person was granted 25,428 restricted stock units on the date of the grant, 12,714 of which are time-based restricted stock units that vest on the third anniversary of the grant date, and 12,714 of which are performance-based restricted stock units that may vest and convert to shares within a range from 0% to 175% of the underlying performance-based restricted stock units originally awarded, depending on our compensation committee approved performance metrics. Vested shares, if any, will be delivered to the reporting person in 3 to 5 business days from the date of vesting.

F2: Represents shares held by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 8,946 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

F3: Included in this total are 75,300 shares held jointly with spouse with a broker, and 74,031 shares held jointly with spouse outright.