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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): November 10, 2025

First Business Financial Services, Inc.

(Exact name of Registrant as Specified in Its Charter)

Wisconsin | 001-34095 | 39-1576570
(State or Other Jurisdiction of Incorporation) | (Commission File Number) | (IRS Employer Identification No.)
401 Charmany Drive |
Madison, Wisconsin |  | 53719
(Address of Principal Executive Offices) |  | (Zip Code)

Registrant’s Telephone Number, Including Area Code: 608 238-8008

N/A

(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, $0.01 par value |  | FBIZ |  | 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. ☐

Item 7.01. Regulation FD Disclosure.

On November 10, 2025, First Business Financial Services, Inc. (the “Company”) posted an investor presentation to its website www.firstbusiness.bank under the “Investor Relations” tab. The information included in the presentation provides an overview of the Company’s recent operating performance, financial condition, and business strategy. The Company intends to use this presentation from time to time when the Company's executives interact with shareholders, analysts and other third parties. A copy of the registrant’s presentation is attached hereto as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

The information in this Current Report on Form 8-K and Exhibit 99.1 attached hereto are being “furnished” pursuant to Item 7.01 of Form 8-K, and will not, except to the extent required by applicable law or regulation, be deemed “filed” by the Company for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor will any of such information or exhibits be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, except as expressly set forth by specific reference in such filing.

Item 9.01. Financial Statements and Exhibits.

(a) Not applicable

(b) Not applicable

(c) Not applicable

(d) Exhibits. The following exhibit is being furnished herewith:

99.1 |  | Slides from Investor Presentation.
104 |  | Cover Page Interactive Data File (embedded within the Inline XBRL Document)

SIGNATURES

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.

November 10, 2025 |  |  |  | F IRST B USINESS F INANCIAL S ERVICES, I NC.
|  |  |  | By: |  | /s/ Brian D. Spielmann
|  |  |  | Name: |  | Brian D. Spielmann
|  |  |  | Title: |  | Chief Financial Officer