UCLA wanted to get off to a good start against sixth-ranked California.
However, after falling behind by 19 points, the 15th-ranked Bruins made a push in the second half, but it wasn't nearly enough to avoid their first home loss in conference play this season.
Gennifer Brandon scored 16 points to lead a balanced offense to help the Bears (22-2, 12-1) get their 10th straight win, 79-51 over UCLA on Friday night.
UCLA coach Cori Close said the Bears were the more aggressive team — Cal had 15 steals in the game, including 10 by Brittany Boyd — and never allowed the Bruins to get into its game.
"We said in the locker room, we have to punch first," Close said. "When you start that slow and that flat, it is really hard to get revved back up."
Atonye Nyingifa scored 20 points for UCLA (19-5, 10-3), which had won six straight since a loss at California on Jan. 20. The Bruins shot just 34 percent (19 for 56) from the field.
The Bears built their 19-point lead in the first half and led by 18 at the break. UCLA made an early run in the second half in an effort to cut into Cal's halftime lead. Nirra Fields had a steal and dribbled the length of the court to score and pull the Bruins to 47-36 with 13:57 remaining. But they could get no closer the rest of the way.
"It was a big game for us," Nyingifa said. "It's disappointing to lose, especially one we felt we had to win. But we have to get ready to play another game (Sunday against No. 4 Stanford)."
Boyd and Layshia Clarendon had 14 points each for California, and Reshanda Gray added 10.
The Bruins started slowly, missing their first five field-goal attempts and allowing Cal to jump out to an 11-6 lead after a basket by Clarendon, her only two points of the first half.
"It was important to set the tone," Cal coach Lindsay Gottlieb said. "UCLA is talented, they're tough, they're aggressive and they're physical. That's what they do, they overpower people. We thought it was important from the beginning to send a message, that's not going to happen tonight."
UCLA pulled to 11-10 after an outside shot by Kacy Swain, but the Bruins' poor shooting in the first half cost them. UCLA shot only 29 percent (9 for 31) in the opening 20 minutes.
Alyssia Brewer and Markel Walker, two of the Bruins' top three scorers averaging a combined 22.7 points per game, went scoreless in the first half, shooting a combined 0 for 7 from the field. Nyingifa's 10 points led the Bruins at the half.
The Bears had balanced scoring in the opening half as all eight who played scored at least two points. Brandon led the way with 10 points and Gray had eight.
Cal finished the first half strong. After the Bruins pulled to 20-16 with 7:01 to play, the Bears got hot, taking their biggest lead of the half at 37-18 lead on a 3-pointer by Mikayla Lyles with 52 seconds until the break.
Brandon's outside jumper at the buzzer gave the Bears a 39-21 lead at the half.
Cal hasn't lost since a defeat to No. 4 Stanford on Jan. 8.
"We want to become part of the nation's elite," Gottlieb said. "We want to make a name for ourselves. But you do that by taking one small step at a time and taking care of the business in front of you. But those increments, I hope, are saying we're for real on the national level."