UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13A-16 OR 15D-16 OF THE

SECURITIES EXCHANGE ACT OF 1934

For the month of April 2026

Commission File Number: 001-41889

CADELER A/S

(Translation of registrant's name into English)

Kalvebod Brygge 43

DK-1560 Copenhagen V, Denmark

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F x Form 40-F o

Stock Exchange Announcement

CADELER A/S: Notification of major shareholding

Copenhagen, 1 April 2026: Cadeler A/S (OSE: CADLR, NYSE: CDLR) (“Cadeler”) hereby announces that it has received the following major shareholder notification pursuant to Section 38 of the Danish Capital Markets Act and Section 55 of the Danish Companies Act, respectively, regarding direct and indirect holdings of shares in Cadeler.

Folketrygdfondet’s direct shareholding in Cadeler has been reduced due to dilution resulting from the issuance of 35,095,758 new shares as part of a private placement in Cadeler (the “Private Placement”). Reference is made to the stock exchange announcement published by Cadeler on 26 March 2026 regarding the results of the Private Placement. Folketrygdfondet’s direct shareholding in Cadeler continues to be 18,462,464 shares of a nominal value of DKK 1 each, corresponding to 4.78% of Cadeler’s total share capital and voting rights following the capital increase carried out in connection with the Private Placement.

Folketrygdfondet manages the Government Pension Fund Norway (GPFN) at the behest of the Norwegian Ministry of Finance and the activities of Folketrygdfondet are governed by Act of 29 June 2007 No. 44 relating to Folketrygdfondet. Folketrygdfondet is organised under the laws of Norway under the registration number 971 525 061 with its registered address at Haakon VIIs gate 2, Postboks 1845 Vika, 0123 Oslo, Norway.

For further information, please contact:

Mikkel Gleerup

CEO, Cadeler

+45 3246 3102

mikkel.gleerup@cadeler.com

Alexander Simmonds

EVP & CLO, Cadeler

+44 7376 174172

alexander.simmonds@cadeler.com

About Cadeler A/S:

Cadeler is a global leader in offshore wind installation, operations, and maintenance services. Cadeler is a pure play company, operating solely in the offshore wind industry with an uncompromising focus on safety and the environment. Cadeler owns and operates the industry’s largest fleet of jack-up offshore wind installation vessels and has for more than 10 years been a key supplier in the development of offshore wind energy to power millions of households. Cadeler’s fleet, expertise and capacity to handle the largest and most complex next-generation offshore wind installation projects positions the company to deliver exceptional services to the industry. Cadeler is committed to being at the forefront of sustainable wind farm installation and to enabling the global energy transition towards a future built on

renewable energy. Cadeler is listed on the New York Stock Exchange (ticker: CDLR) and the Oslo Stock Exchange (ticker: CADLR).

For more information, please visit www.cadeler.com.

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, thereunto duly authorized.

Date: April 1, 2026 CADELER A/S

(Registrant)

By: /s/ Mikkel Gleerup
Name:     Mikkel Gleerup
Title:    Chief Executive Officer

Cadeler A/S 6-K