Company Update

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C.  20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 23, 2026 1st Source Corp oration (Exact name of registrant as specified in its charter) Indiana 0-6233 35-1068133 (State or other jurisdiction of incorporation) (Commission File No.) (I.R.S. Employer Identification No.) 100 North Michigan Street , South Bend , Indiana 46601 (Address of principal executive offices)     (Zip Code) 574 - 235-2000 (Registrant's telephone number, including area code) Not Applicable (Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions: ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock - without par value SRCE The NASDAQ Stock Market LLC Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o ITEM 8.01      Other Events. On February 23, 2026, Christopher J. Murphy III, Executive Chairman of 1st Source Corporation (the “Company”) and 1st Source Bank (the “Bank”) announced to shareholders of the Company that he is undergoing cancer treatment and plans to work remotely for at least the next nine weeks. A copy of the announcement is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference into this Item 8.01. ITEM 9.01      Financial Statements and Exhibits. (d) Exhibits: 99.1     Letter to Shareholders of the Company drafted on February 23, 2026 by Christopher J. Murphy III, Executive Chairman of the Board of the Company and the Bank. 104    Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. 1st SOURCE CORPORATION (Registrant) Date: February 23, 2026 /s/ Brett A. Bauer Brett A. Bauer Treasurer and Chief Financial Officer Principal Accounting Officer