Mickelson had a legitimate chance to fire the lowest round in the history of the PGA Tour, needing birdies on his final two holes at the TPC-Scottsdale course to turn in a 58.
His birdie putts on the two closing holes combined to miss by no more than two inches -- the first one stopping just short of the cup and the second one spinning out after appearing to be perfect all the way.
Mickelson's 60 was the first shot on the tour this year and left him at 11-under par after the opening round.
On a perfect day for golf, Ryan Palmer, Padraig Harrington, Ted Potter, Jeff Maggert and Brandt Snedeker all shot 64 to share second place. Bill Haas and major championship winners Y.E. Yang and Justin Leonard were among those at 65, as was recent Humana Challenge champion Brian Gay.
Current Masters champ Bubba Watson, returning to the tour after a two-week illness that left him 10 pounds lighter, shot a 67.
Mickelson began play at the 10th hole Thursday and birdied the first four holes en route to a 29 on the back nine.
He made four more birdies on the front side and came to the par-4 eighth, his 17th hole of the day, with a good chance to make golfing history. The only 59s ever shot on the tour have been turned in by Al Geiberger (1977), Chip Beck (1991), David Duval (1999), Paul Goydos (2010) and Stuart Appleby (2010).
Mickelson hit his second shot at the eighth to within 17 feet and the downhill putt stopped on the lip of the cup.
"It was going in the hole," Mickelson said. "I didn't think there was any way I could leave it short, but I guess there was a way."
At the par-4 ninth, Mickelson put his second shot 25 feet from the hole. As that putt neared the cup, Mickelson took a few steps toward the hole and extended his putter in the classic pose of a golfer who is certain the ball is going to go in.
Instead, it caught the right lip of the cup, spun halfway into the hole and then lipped out on the left side.
"Six feet from the hole it was going right in the middle," Mickelson said. "That one will be tough to take because you don't get many chances to do that (shoot 59). I'm excited about the 60, but you don't get that kind of opportunity very often."