Freshman guard Lonzo Ball led both teams in turnovers, accounting for seven of UCLA's 17 total.
Junior forward Thomas Welsh got off to an early start, going 6-for-6 in the first half and scoring 13 points, but he remained scoreless in the second half.
USC freshman forward Nick Rakocevic celebrates USC's 12-point lead at the half.
Junior point guard Jordan McLaughlin led the unranked Trojans to an eight-point upset of the No. 8 Bruins.
Freshman forward T.J. Leaf pulled down eight rebounds, but got into foul trouble in the second half with four personal fouls.
The Trojans shot 14-for-34 from 3-point line compared to the Bruins' 6-for-20.
Sophomore guard Aaron Holiday scored 15 points but contributed four turnovers against USC.
Senior guard Bryce Alford played 37 minutes against the Trojans while going 1-for-7, scoring his only points off a 3 in the final minutes of the game.
Welsh led both teams with three blocks, but the Trojans still led the game for 27 minutes, 18 seconds.
Ball went 5-for-9 from the free throw line in UCLA's first back-to-back loss of the season.
USC's bench celebrates as sophomore guard Shaqquan Aaron scored a career-high 23 points.
USC fans celebrate their fourth win in a row against the UCLA men's basketball team.