Nowell finished with a game-high 23 points, and Noah Dickerson added 16 for the Huskies (19-10, 9-7 Pac-12), who managed a split of their games in the San Francisco Bay Area after Thursday's 94-73 loss at Stanford.
Washington completed a season-series sweep of Cal, having earned a 66-56 home win last month.
Darius McNeill had a team-high 17 points for the Bears (8-21, 2-14), who lost their fifth straight and equalled the school record for losses in a season, set initially in 1979, when Cal went 6-21.
After a tight first half in which there were four lead changes and four ties, the Huskies trailed 43-39 following a Don Coleman jumper for the Bears at the 16:32 mark.
Washington followed with its 9-0 burst, which was capped by Nahziah Carter's three-point play that extended the Huskies' lead to 48-43.
The Washington defense took care of things from there, holding Cal to two field goals in 19 attempts the rest of the way after Coleman's hoop.
Cal missed its final eight shots, including six 3-pointers, and finished the game shooting 34.0 percent. The Bears were held under 60 points for the eighth time in conference play this season.
Nowell used 13-for-14 success at the free throw line to accumulate a majority of his points for the Huskies, who shot 45.7 percent from the field and outscored Cal 21-12 on 3-pointers.
Matisse Thybulle did all his scoring on 3-pointers, hitting three for nine points.
Dickerson had a game-high nine rebounds to complement his 16 points for Washington, which allowed the fewest points in any of its games this season.
McNeill made three 3-pointers for Cal, but his teammates combined for just one during a 4-for-17 team performance.
Justice Sueing added 12 points for Cal, while Coleman finished with a game-high four assists to go with eight points.
--Field Level Media
Washington | California | |
Jaylen Nowell 23 | Scoring | Darius McNeill 17 |
Nahziah Carter 3 | Assists | Don Coleman 4 |
Noah Dickerson 9 | Rebounds | Roman Davis 5 |
Jaylen Nowell 13 | Free Throws Made | Don Coleman 6 |
Matisse Thybulle 2 | Steals | Don Coleman 6 |
Noah Dickerson 2 | Blocks | Marcus Lee 2 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Washington | 68 | 44.7 | 7-17 | 19-24 | 11 | 29 | 4 | 3 | 17 |
California | 51 | 34.6 | 4-16 | 11-15 | 7 | 27 | 5 | 10 | 17 |