Mickelson carded five birdies in the final round at TPC Scottsdale's Stadium Course to end at 28-under 256, which tied for the second-lowest score ever in a 72-hole PGA Tour event.
The left-hander just missed notching a 59 in Thursday's first round and never trailed in taking the Phoenix event for the third time. He also won it 1996 and 2005.
Brandt Snedeker claimed second place at 24-under with a round of 6-under 65.
Scott Piercy charged into sole possession of third place at minus-23 with a 10-under 61 Sunday.