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 September 2025

Commission File Number: 001-15092

TURKCELL İLETİŞİM HİZMETLERİA.Ş.

(Translation of registrant’s name into English)

Turkcell Küçükyalı Plaza

Aydınevler Mahallesi İnönü Caddesi No:20

Küçükyalı 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 September 24, 2025 announcing the registrant's participation in an ICTA tender

Istanbul, September 24, 2025

Announcement Regarding Participation in theICTA Tender

Our Company’s Board of Directors has resolved to participate in the tender to be held by the Information and Communication Technologies Authority (ICTA) on October 16, 2025, regarding the “Authorization for the Establishment and Operation of Mobile Electronic Communication Infrastructures and the Provision of Services, and the Inclusion of Infrastructures and Services under Existing Authorizations Expiring on April 30, 2029, Within the Scope of This Authorization.”

For more information:

Turkcell Investor Relations

investor.relations@turkcell.com.tr

Tel: + 90 212 313 1888

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.