Sertdemir is a youth product of Brøndby and moved to the academy of Nordsjælland at the age of 12.
[2] He then joined German club Bayer Leverkusen on 15 June 2021, signing a three-year contract.
[2] He made his senior debut with Bayer Leverkusen in a 1–1 Bundesliga tie with Hertha on 7 November 2021.
[3] At 16 years and 276 days, Sertdemir is the youngest ever debutant for Bayer Leverkusen in the Bundesliga overtaking his teammate Iker Bravo in the same match, and the second-youngest debutant in the league after Youssoufa Moukoko.
[4] Having not managed to break through Bayer's first team on a full basis, on 31 January 2023 Sertdemir officially returned to Nordsjælland, joining the club on a permanent deal.