Johnson played in 27 games during his freshman season with the
USC Trojans, averaging 1.2 points and one rebound per game. He became a starter as a sophomore and averaged 9.2 points and 5.0 rebounds per game while being named to the
Pac-12 Conference All-Defensive team. Johnson repeated as a Pac-12 All-Defensive Team selection as a junior while averaging 10.9 points, 4.6 rebounds, 3.3 assists, and 2.2 steals per game. After the season, he entered the
NCAA transfer portal. Johnson transferred to the
UCLA Bruins, the
Trojans' crosstown rival. He averaged 7.9 points, 5.9 rebounds, 2.9 assists, and 1.6 steals per game. Johnson was named to the
Big Ten All-Defensive Team for the
2024–25 season. ==Professional career==