Trier, a 6-foot-5 guard, has not played in any of the teams 19 games after testing positive for a performance-enhancing drug. He filed for an appeal with the NCAA -- and won -- however was not cleared to play until the substance was completely out of his system, according to a report by CBS Sports' Gary Parrish earlier this week.
"The NCAA notified us on Friday afternoon that Allonzo Trier's most recent drug test was negative," Arizona said in a statement. "Therefore, he is eligible to return to the court immediately and will be available for our game against UCLA."
As a freshman last season, Trier was among the team's most important contributors, averaging 14.8 points and 28 minutes per game.
Arizona, ranked No. 14 in the AP poll, is 17-2 overall and 6-0 in Pac-12 play headed into Saturday's matchup with the Bruins that will be aired on CBS.