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 June 2026

Commission File Number: 001-15092

TURKCELL İLETİŞİM HİZMETLERİ A.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 June 22, 2026 announcing the amendment to the Long-Term Loan Agreement with China Development Bank.

Istanbul, June 22, 2026

Announcement Regarding the Amendment to the Long-Term Loan Agreement

In reference to our Company's announcement dated March 28, 2025, the second tranche of RMB 1.23 billion of the total RMB 2.46 billion credit package signed with China Development Bank ("CDB") has been revised as RMB 700 million. The annual fixed interest rate including expenses, which may vary depending on the utilization amount and timeline, has been updated from 4.98% to 4.30% for the tranche.

There has been no change in the maturity and the repayment schedule of the loan.

For more information: 

Turkcell Investor Relations

investor.relations@turkcell.com.tr

Tel: + 90 212 313 1888

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.