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 16, 2023      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 8.01 Other Events. On February 16, 2023, MDU Resources Group, Inc. (the “Company”) issued a press release announcing that the Company’s board of directors has selected the management team who will lead Knife River Corporation (“Knife River”), the Company’s construction materials subsidiary, effective upon completion of the anticipated separation of Knife River into an independent, publicly traded company. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. Item 9.01. Financial Statements and Exhibits. (d)    Exhibits. The following exhibits are being furnished as part of this report. Exhibit Number Description 99.1 Press release of MDU Resources Group, Inc., dated Februar y 16 , 2023. 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: February 16, 2023 MDU Resources Group, Inc. By: /s/ Karl A. Liepitz Karl A. Liepitz Vice President, General Counsel     and Secretary 3