Cooper's rookie season with the Celtics was difficult. He was often subjected to racism and discrimination from fans and players alike. However, he persevered and played two seasons with the Celtics, averaging 6.3 points and 5.9 rebounds per game.

After leaving the Celtics, Cooper played for the Milwaukee Hawks and the Fort Wayne Pistons. He retired from the NBA in 1956.

Cooper's career was relatively short, but his impact on the NBA was significant. He paved the way for other African-American players to enter the league, and he helped to break down racial barriers in the sport.