The Turkish international is a midfielder who is known for his passing, vision, ball progression, and shooting. He was born and brought up in the Netherlands, but his family is of Turkish descent. He has capped for the Netherlands Under-18s and Under-19s, but he showed his intent to play for Turkey. He graduated from the Feyenoord football academy, and later he joined SL Benfica. He played a key role in both teams.
The Turkish international is a youth product of FC Groningen, where he arrived after having played for some local clubs around his hometown of Harlem. In 2014, Kokcu took admission in Feyenoord's youth academy, and, at the age of 17, he joined Feyenoord's senior team. He made his debut for Feyenoord in a 4-0 win over VV Gemert in the first round of the KNVB Cup on 17 September 2019. He made his Eredivisie debut against FC Emmen on 9th December, 2018, and contributed with a goal and an assist, despite coming on as a substitute. On 10th April, 2019, he extended his contract with Feyenoord until 2023. In 2022, Arne Slot became the head coach of Feyenoord, and Slot made him the club's captain. With Kokcu as a captain, Feyenoord went on to win that 2022-23 season.
On 10th June, 2023, after winning the Eredivisie trophy with Feyenoord, his playing style caught the attention of a Portuguese side, SL Benfica. Orkun joined SL Benfica on a record €25 million and an extra €5 million variables, with a 4.5-year contract. The sum represented a record signing for a Portuguese side, surpassing Darwin Nunez's transfer fee. The Turkish international made his debut for the Portuguese side in the Supertaca Candido de Oliveira, starting in a 2-0 win over their fierce rival FC Porto. Oscar made his UEFA Champions League debut against Red Bull Salzburg with a 2-0 loss at home.
Kokcu was a youth international for the Dutch national team, having represented the Dutch national team in the Under-18s and Under-19s. In July 2019, Kokcu announced that he wanted to join the Turkish national team. He represented the Turkish team in the Under-21s in a 3-2 w=2021 UEFA Under-21s Championship qualification loss to England under-21s on 6th September 2019. He made his Turkey national team debut on 6th September 2020, in a Nations League game against Serbia. He started the game and played the first hour of the 0-0 draw.
Orkun Kokcu has won the Eredivisie title with Feyenoord in the 2022&23 season, and won the Portuguese Super Cup title with SL Benfica. He was also named player of the year in the 2022/23 season after contributing to 11 goals in just 31 matches.