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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): April 21, 2026

Mercantile Bank Corporation
(Exact name of registrant as specified in its charter)

Michigan | 000-26719 | 38-3360865
(State or other jurisdiction of incorporation) | (Commission File Number) | (IRS Employer Identification Number)

310 Leonard Street NW, Grand Rapids, Michigan | 49504
(Address of principal executive offices) | (Zip Code)
Registrant's telephone number, including area code | 616-406-3000

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 (see General Instruction A.2. below):
☐ 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 | MBWM | 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 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).
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 2.02 | Results of Operations and Financial Condition.

Earnings Release
On April 21, 2026, Mercantile Bank Corporation (the “Company”) issued a press release announcing earnings and other financial results for the quarter ended March 31, 2026. A copy of the press release is furnished as Exhibit 99.1 to this report and incorporated here by reference.

Item 7.01 | Regulation FD Disclosure.

The Company has prepared presentation materials (the “Conference Call & Webcast Presentation”) that management intends to use during its previously announced First Quarter 2026 conference call on Tuesday, April 21, 2026 at 10:00 am Eastern Time, and from time to time thereafter in presentations about the Company’s operations and performance. The Company may use the Conference Call & Webcast Presentation, possibly with modifications, in presentations to current and potential investors, analysts, lenders, business partners, acquisition candidates, customers, employees and others with an interest in the Company and its business.
A copy of the Conference Call & Webcast Presentation is furnished as Exhibit 99.2 to this report and incorporated here by reference. The Conference Call & Webcast Presentation is also available on the Company's website at http://ir.mercbank.com. Materials on the Company’s website are not part of or incorporated by reference into this report.
In accordance with General Instruction B.2 of Form 8-K, the information in this Current Report on Form 8-K, including Exhibits 99.1 and 99.2, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liability of that section, and shall not be incorporated by reference into any registration statement or other document filed under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.

Item 9.01 | Financial Statements and Exhibits.

(d) Exhibits.
Exhibit Number Description

99.1 | Press release of Mercantile Bank Corporation dated April 21, 2026, reporting financial results and earnings for the quarter ended March 31, 2026.

99.2 | Mercantile Bank Corporation Conference Call & Webcast Presentation dated April 21, 2026.

104 | Cover Page Interactive Data File (embedded within the Inline XBRL document)

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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.

| Mercantile Bank Corporation |
| By: | /s/ Charles E. Christmas |
|  | Charles E. Christmas |
|  | Executive Vice President, Chief |
|  | Financial Officer and Treasurer |

Date: April 21, 2026
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