TKC 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 June 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 June 24, 2026 announcing the registrant’s financing bond issuance.

Istanbul, June 24, 2026

Announcement Regarding the Financing Bond Issuance

Within the scope of the TRY 15,000,000,000 issuance limit approved by the Capital Markets Board, the book building of the financing bond issuance of our Company with a maturity date of September 25, 2026, an annual simple interest of 40.25% with a nominal amount of TRY 500,000,000 to qualified investors within Türkiye, without a public placement was completed, and the securities will be transferred to the investor accounts on June 24, 2026 (today).

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Redemption Plan of Capital Market Instrument Sold

* The date on which the beneficiaries are determined.

Issuer Rating Note

For more information:

Turkcell Investor Relations

[email protected]

Tel: + 90 212 313 1888

Disclaimer

This press release does not constitute an offer to sell, or a solicitationof offers to purchase or subscribe for securities in the United States or any other jurisdiction in which such offer or solicitationwould 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, USpersons (as defined in Regulation S under the Securities Act) absent registration or an applicable exemption from the registration requirementsof the Securities Act. This press release is being issued pursuant to and in accordance with Rule 135c under the Securities Act.

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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.