Reg FD Disclosure

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): March 13, 2024 MDU Resources Group Inc (Exact name of registrant as specified in its charter) (State or other jurisdiction of (Commission File Number) (I.R.S. Employer Identification No.) incorporation) Delaware 1-03480 30-1133956 1200 West Century Avenue P.O. Box 5650 Bismarck , North Dakota 58506-5650 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code ( 701 ) 530-1000 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 Securities Exchange Act of 1934: (Title of each class) (Trading Symbol(s)) (Name of each exchange on which registered) Common Stock, par value $1.00 per share MDU New York Stock Exchange Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 or Rule 12b-2 of the Securities Exchange Act of 1934. 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 March 13, 2024, MDU Resources Group, Inc. issued a press release affirming its 2024 financial guidance and providing an updated long-term earnings per share growth rate outlook. A copy of the press release is attached as Exhibit 99.1 hereto and incorporated by reference herein. The information in this Item 7.01, including Exhibit 99.1, 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 of that section, nor shall such information, including Exhibit 99.1, be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing. The information set forth herein, including Exhibit 99.1, will not be deemed an admission as to the materiality of any information required to be disclosed solely to satisfy the requirements of Regulation FD. Item 9.01. Financial Statements and Exhibits. (d) Exhibits. Exhibit Number Description 99.1 Press release of MDU Resources Group, Inc., dated March 13, 2024. 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). 2 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. Date: March 13, 2024 MDU Resources Group, Inc. By: /s/ Paul R. Sanderson Paul R. Sanderson Vice President, Chief Legal Officer     and Secretary 3