Shabazz Muhammad netted 23 points and the UCLA Bruins handed No. 6 Arizona its first home loss in an 84-73 decision at McKale Center.
David Wear and Jordan Adams, who went without a field goal in a loss to Oregon last Saturday, each chipped in 15 points for the Bruins (16-4, 6-1 Pac-12) in their first road win against their Pac-12 rival since March 2, 2008.
Arizona (16-2, 4-2) got 23 points from Nick Johnson and 16 from Mark Lyons, but never fully recovered from a slow start.
The Wildcats shot just 31 percent (11-of-35) in the first half and found themselves down by as many as 15 after the break.
They got hot during a two-minute stretch in the middle stages of the second half to cut a 14-point deficit down to four with a 10-0 run. Johnson started the string with a 3-point play and ended it with a two-handed slam in transition to get within 55-51.
That was the closest Arizona got, however. Muhammad made a 3-pointer then forced a turnover that led to two free throws for a 65-58 lead with under 5 1/2 minutes to play.
The Wildcats missed several 3-point attempts down the stretch and finished 5- of-24 from behind the arc as UCLA sealed the win at the free throw line.
"Sometimes when we play behind the whole game we try to make things happen individually," Arizona head coach Sean Miller said. "Even though our guys fought hard, we weren't playing team basketball or executing."
Arizona made just one field goal over the final 7 1/2 minutes, and a 12-0 run had the Bruins on top, 19-3.
A late Grant Jerrett pulled the Wildcats within 35-30, but a layup by Larry Drew II and a three-point play by Kyle Anderson over the final two minutes pushed UCLA's advantage to double-digits at the break.
Consecutive jumpers by Adams gave the visitors their biggest lead, 49-34, four minutes into the second half.
The Bruins' previous victory on the road against ranked team came Feb. 7, 2008 at No. 17 Washington State ... Solomon Hill posted 13 points and 10 rebounds for the Wildcats, who had just 10 assists on 28 made field goals ... Anderson pulled down a game-high 12 rebounds.