Mickelson shot a 4-under 67 on Sunday to finish at 28-under 256, two strokes off the PGA Tour record of 254 set by Tommy Armour III in the 2003 Texas Open.
Mickelson missed a chance for a 59 in the first round when his 25-foot birdie putt on the final hole caught the right edge of the cup, curled 180 degrees and stayed out. He settled for a 60 and followed with rounds of 65 and 64 to take a six-stroke lead into the final round.
Brandt Snedeker finished second, four strokes back after a 65.
Mickelson took a three-stroke lead to the 17th tee, and nearly drove into the left-side water on the drivable par 4, his ball stopping a yard short of the hazard. He hit his 25-yard second shot 15 feet past the hole and made the birdie putt. Snedeker matched him with a little shorter putt to remain three shots behind.
Mickelson parred the par-4 18th after another drive to the left, one that easily cleared the water he hit into Friday en route to a double bogey. Snedeker closed with a bogey.
Mickelson had his third wire-to-wire victory and first since the 2006 BellSouth Classic — a 13-stroke blowout the week before the second of his three Masters victories. He pushed his victory total to 41, winning for the first time since 51 weeks ago at Pebble Beach.
Making his 24th appearance in the event that he also won in 1996 and 2005, Mickelson tied the tournament scoring record set by Mark Calcavecchia in 2001, and joined Calcavecchia, Arnold Palmer and Gene Littler as the only three-time winners. With six victories in Arizona, Mickelson also matched Johnny Miller’s tour record.
Mickelson won after struggling the last two weeks in his season-opening events — tying for 37th at La Quinta and 51st at Torrey Pines — and causing a sensation by talking about tax increases. He now heads to Pebble Beach for his title defense.
After three nearly cloudless days in the Valley of the Sun, the final round was played in overcast conditions. Light rain even fell for a few minutes as Mickelson finished warming up on the practice green and played the first hole.
After the rain stopped, Mickelson bogeyed the par-4 second hole and birdied the two front-nine par 3s, pulling off his best shot of the day on No. 7.
After Snedeker, four strokes back after a birdie on No. 6, hit within 10 feet of the back-left pin to set up a birdie, Mickelson’s tee shot leaked right and rolled to a stop an inch from the back fringe, leaving him 55 feet with a 20-foot swath of fringe between his ball and the hole.
Mickelson decided to putt through the fringe rather than chip over it and had caddie Jim Mackay remove the flagstick. The 42-year-old former Arizona State star hit it perfectly, with the ball avoiding the rough, rolling back onto the green and racing into the cup.
Mickelson pushed the advantage back to four strokes with a two-putt birdie on the par-5 13th, his fourth straight birdie on the hole. Snedeker saved par on the hole after his drive stopped under jumping cholla, forcing him to take a drop for an unplayable lie.
Mickelson matched Snedeker on the next two holes, saving par on the par-4 14th with a 10-foot putt and two-putting for birdie on the par-5 15th.
Snedeker pulled within three again on the par-3 16th, hitting to 5 feet on the stadium hole. Mickelson’s 15-footer slid by the right edge.
Snedeker had his second second-place finish of the week. He tied for second Monday at Torrey Pines, four strokes behind Tiger Woods in the fog-delayed event.
Scott Piercy shot a 61 to finish third at 23 under. Ryan Moore was fourth at 22 under after a 65, and Ryan Palmer closed with a 62 to finish fifth at 19 under.