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 May 2025

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 ¨

Stock exchange announcement

CADELER A/S: COMPLETION OF SHARE BUY-BACK PROGRAMME AND DISCLOSURE OF REPURCHASE TRANSACTIONS MADE UNDER THE SHARE BUY-BACK PROGRAMME

Copenhagen, 30 May 2025: Cadeler A/S (OSE: CADLR, NYSE: CDLR) (“Cadeler”) today confirms that it has completed the share buy-back programme it announced on 26 May 2025 in advance of the programme’s anticipated termination date of 6 June 2025, as the maximum number of shares to be repurchased under the programme was reached earlier than that date. The share buy-back programme has therefore been terminated early.

Between 26 May 2025 and 30 May 2025, Cadeler repurchased 395,200 of its own shares at an average price per share of NOK 49.92, corresponding to an aggregate purchase price of NOK 19,728,604, or approximately EUR 1.7 million.

On 26 May 2025, Cadeler initiated a share buy-back programme of up to NOK 22.5 million (approx. EUR 1.9 million) to enable Cadeler to meet its obligations to its employees arising from certain of Cadeler’s share-based incentive programmes (the “Programme”) in accordance with Article 5 of Regulation (EU) no. 596/2014 of the European Parliament and of the Council of 16 April 2014, as amended (the “Market Abuse Regulation”), and the Commissions Delegated Regulation (EU) 2016/1052 of 8 March 2016 (together with the Market Abuse Regulation, the “Safe Harbour Rules”). Further details on the terms of the Programme can be found in Cadeler’s stock exchange announcement dated 26 May 2025.

The following transactions were made under the Programme between the commencement of the Programme on 26 May 2025 and 30 May 2025:

¹ EUR figures presented based on the prevailing NOK/EUR exchange rate on 30 May 2025.

Details of each transaction made under the Programme are attached as an appendix to this stock exchange announcement.

Following the conclusion of the Programme Cadeler holds a total of 478,345 shares in treasury, each with a nominal value of DKK 1.00 and corresponding in the aggregate to less than 0.1% of Cadeler’s total share capital and voting rights of Cadeler, as treasury shares.

For further information, please contact:

Mikkel Gleerup, CEO

+45 3246 3102

mikkel.gleerup@cadeler.com

Alexander Simmonds, EVP & CLO

+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.

Appendix: Disclosure of transaction data under the share repurchase programme for Cadeler A/S in the period 26 May 2025 to 30 May 2025

This document discloses the transactions made under the share repurchase programme for Cadeler A/S in the period 26 May 2025 to 30 May 2025 in a detailed and aggregated form in accordance with Commission Delegated Regulation (EU) 2016/1052 of 8 March 2016 supplementing Regulation (EU) No. 596/2014 of the European Parliament and of the Council of 16 April 2014, as amended, with regards to regulatory technical standards for the conditions applicable to buy-back programmes and stabilisation measures.

¹ EUR figures presented based on the prevailing NOK/EUR exchange rate on 30 May 2025.