Büyüktuncel was born and grew up in Bursa, Turkey.[1] He played for the youth teams of Tofaş S.K.[2] Büyüktuncel averaged 11.4 points, 8.5 rebounds, 2.2 assists, 1.5 steals, and 1.5 blocks for the Under-19 team and made his Basketbol Süper Ligi debut with the senior team during the 2020–2021 season.[3]
College career
Büyüktuncel committed to play college basketball in the United States for UCLA and signed a National Letter of Intent on August 5, 2023.[4] He enrolled at UCLA in September 2023 after being granted his release from Tofaş. Büyüktuncel was not declared eligible to play by the NCAA before the start of the Bruins' 2023–24 season.[5] He was cleared to play three games into the season.[6] Hampered by injuries and uneven play, he averaged 4.5 points and 2.5 rebounds in 16.3 minutes per game.[7]