Harvick held off Kyle Busch to end a 44-race winless streak in Sprint Cup action at the wild Phoenix event, which featured a multi-car accident in the final laps that triggered a brawl between the crews of drivers Jeff Gordon and Clint Bowyer.
Keselowski, however, avoided the incident and crossed the finish line to take sixth place and establish a lead over Jimmie Johnson, who came into Sunday with a seven-point advantage in the championship Chase standings.
Johnson was involved in another wreck in which he hit the wall on lap 234, sustaining suspension damage that took 38 laps to repair. He ended in 32nd place.
Fights between the Gordon and Bowyer crews broke out on pit road after the two drivers collided late in the race.