6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TORULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of April 2025

Commission File Number: 001-40552

NYXOAH SA

(Translation of registrant’s name into English)

Rue Edouard Belin 12, 1435 Mont-Saint-Guibert,Belgium

(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 ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ¨

Note: Regulation S-T Rule 101(b)(1) only permits the submission in paper of a Form 6-K if submitted solely to provide an attached annual report to security holders.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ¨

Note: Regulation S-T Rule 101(b)(7) only permits the submission in paper of a Form 6-K if submitted to furnish a report or other document that the registrant foreign private issuer must furnish and make public under the laws of the jurisdiction in which the registrant is incorporated, domiciled or legally organized (the registrant’s “home country”), or under the rules of the home country exchange on which the registrant’s securities are traded, as long as the report or other document is not a press release, is not required to be and has not been distributed to the registrant’s security holders, and, if discussing a material event, has already been the subject of a Form 6-K submission or other Commission filing on EDGAR.

Nyxoah SA

On April 16, 2025, Nyxoah SA (the “Company”) issued a press release, a copy of which is attached hereto as Exhibit 99.1.

The information in the attached Exhibit 99.1is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that Section, nor shall it be deemed incorporatedby reference in any filing made by the Company under the Securities Act of 1933, as amended, or the Exchange Act, except as otherwiseset forth herein or as shall be expressly set forth by specific reference in such a filing.

Exhibits

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.

Exhibit 99.1

INSIDE INFORMATION

REGULATED INFORMATION

Conditional Issuance of Shares

Mont-Saint-Guibert, Belgium – April 16,2025, 8:00 am CET / 2:00 am ET – Nyxoah SA (Euronext Brussels/Nasdaq: NYXH) (“Nyxoah” or the “Company”), today announced a conditional issuance of up to 5 million ordinary shares under its existing at-the-market equity offering programs (the “ATM”). This brings the aggregate number of ordinary shares that can be sold and issued under the Company’s ATM to 5,662,694 (the “ATM Shares”), which includes 662,694 shares that are still available from the conditional issuance of shares under the ATM decided upon on December 22, 2022.

Pursuant to the existing sales agreement entered into by the Company on December 22, 2022, ATM Shares may be sold from time to time at a sales price per ATM Share equal to prevailing USD market prices of the Nyxoah ordinary share on the Nasdaq Global Market at the time of the sale.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy any securities.

Contacts:

Nyxoah

John Landry, CFO

IR@nyxoah.com

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