6-K

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

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of April 2026

Commission File Number: 001-15092

TURKCELL İLETİŞİM HİZMETLERİA.Ş.

(Translation of registrant’s name into English)

Turkcell Küçükyalı Plaza

Aydınevler Mahallesi İsmet İnönü Caddesi No:20

Küçükyalı B Blok Ofispark

34854 Maltepe

Istanbul, Türkiye

(Address of Principal Executive Offices)

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

x Form 20-F  ¨ Form 40-F

Enclosure: A press release dated April 22, 2026 announcing the registrant's application to the Capital Markets Board for a debt instrument issuance in the domestic market.

Istanbul, April 22, 2026

AnnouncementRegarding the Application to the Capital Markets Board for a Debt Instrument Issuance in the Domestic Market

With reference to our Company’s announcement dated November 6, 2025, we made an application to the Capital Markets Board for the approval of a debt instrument issuance certificate.

For more information:

Turkcell Investor Relations

investor.relations@turkcell.com.tr

Tel: + 90 212 313 1888

Disclaimer

This press release does not constitute an offer to sell, or a solicitation of offers to purchase or subscribe for securities in the United States or any other jurisdiction in which such offer or solicitation would be unlawful. The securities referred to herein have not been and will not be registered under the U.S. Securities Act of 1933, as amended (the ‘‘Securities Act’’), and may not be offered, sold or delivered within the United States or to or for the benefit of, U.S. persons (as defined in Regulation S under the Securities Act) absent registration or an applicable exemption from the registration requirements of the Securities Act. This press release is being issued pursuant to and in accordance with Rule 135c under the Securities Act.

1

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, Turkcell İletişim Hizmetleri A.Ş. has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.