Results of Operations

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: April 30, 2026 MIDDLESEX WATER COMPANY (Exact name of registrant as specified in its charter) New Jersey 0-422 22-1114430 (State or other jurisdiction of incorporation or organization) (Commission File Number) (I.R.S. Employer Identification No.) 485C Route 1 South , Suite 400 , Iselin , New Jersey 08830 (Address of Principal Executive Offices) (Zip Code) 732 - 634-1500 (Registrant’s telephone number, including area code) 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: o     Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) o     Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) o     Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) o     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, No Par Value MSEX 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 o 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 2.02 Results of Operations and Financial Condition. On April 30, 2026, Middlesex Water Company announced its financial results for the quarter ended March 31, 2026. A copy of the press release announcing these results is attached hereto as Exhibit 99.1 and incorporated into this Form 8-K by reference. The information in Item 2.02, including the exhibit, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities under that Section, nor shall it be deemed to be incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing. Item 9.01 Financial Statements and Exhibits. (c) Exhibits Exhibit Number Description of Document 99.1 Press Release issued by Middlesex Water Company dated April 30, 2026 reporting First Quarter 2026 Earnings 104 The cover page from this Current Report on Form 8-K, formatted in Inline XBRL. 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 of the undersigned hereunto duly authorized. MIDDLESEX WATER COMPANY (Registrant) /s/ Mohammed G. Zerhouni Sr. Vice President, Chief Financial Officer and Treasurer Dated: April 30, 2026 2