Korkmaz was a member of the junior national teams of Turkey. With Turkey's junior national teams, he played at: the 2013 FIBA Europe Under-16 Championship, which he led in scoring, the 2014 FIBA Europe Under-18 Championship, where he won a gold medal, the 2015 FIBA Europe Under-18 Championship, where he won a silver medal and was named to the All-Tournament Team, and at the 2015 FIBA Under-19 World Cup, where he won a bronze medal and was named to the All-Tournament Team.