Mitrou-Long began his collegiate career in the NCAA with the Mount St. Mary’s Mountaineers, where during his sophomore season he averaged 15.0 points, 5.2 rebounds and 4.4 assists resulting in multiple honours including All-Northeast Conference (NEC) First Team. He scored 22 points in the NEC championships earning him the tournament MVP title.
After two years with the Mountaineers, Mitrou-Long transferred to the University of Texas, and then went on to the University of Nevada Las Vegas for his senior year averaging 12.6 points, 3.3 rebounds, 3.4 assists and 1.7 steals per game.
Mitrou-Long signed his first professional contract with PAOK of the Greek Basket League and went on to play with Levski Sofia in Bulgaria where he averaged 14 points, 3.5 rebounds and 5.6 assists per game. He made his return to Greece for the 2022 season with Apollon Patras.