Top-seeded Arizona (29-3) had trouble shaking the Bears in a rough first half before taking control with a run early in the second.
Rondae Hollis-Jefferson had 10 points, six rebounds and was the catalyst for Arizona's defense.
T.J. McConnell added 13 points and six rebounds for the Wildcats, who move on to face the winner between USC and UCLA in Friday's semifinals
No. 8 seed Cal (18-15) played better than it did in two blowout losses to Arizona during the regular season, but faded after the Wildcats made their second-half run.
Arizona won its second straight Pac-12 regular-season title and is trying to add something that had been elusive: The conference tournament title.
The Wildcats have reached the title game three times in coach Sean Miller's six seasons, but have not won the championship since 2002, when Luke Walton was tournament MVP.
The first step was to knock off Cal, a team they beat by a combined 62 points in two games this season.
The Bears rolled over Washington State in the opening round with an impressive offensive show and stood toe to toe with Arizona in a physical first half.
Cal didn't shoot particularly well, but grinded the game down to stay within 33-27 at halftime.
Hollis-Jefferson was the spark for Arizona. The athletic forward is always revved up, but seemed to have it in an extra gear against Cal.
He soared in for a tomahawk dunk over Kingsley Okoroh, blocked Wallace from behind and guarded different players on three straight possessions during one stretch.
Hollis-Jefferson also got tangled with Dwight Tarwater, which led to a shove and some jawing, and had to be escorted away by the officials after colliding with two players diving for a loose ball.
Hollis-Jefferson continued to fight for every inch and loose ball, and had a dunk in transition during a 9-0 run that put Arizona up 46-32.
Arizona stretched the lead from there, smothering the Bears defensively to prevent a comeback.
Cal: Kravish and Ashley were called for double technical fouls late in the second half after getting tangled and shoving each other. ... The Bears hit 4 of 14 from 3-point range.
Arizona: The Wildcats made 6 of 11 from 3-point range. ... Johnson and Ashley each had seven rebounds.
Cal has to wait to see if it will get a postseason bid.
Arizona will face the winner between USC and UCLA in Friday's semifinals.