Mickelson, regarded as one of the leading players yet to win a major, was four shots off the pace heading into the third round of the USPGA Championship. However, his challenge collapsed with an eight-over 78. He rebounded with a 67 on Sunday, but it not enough.
Playing the Pebble Beach course, Mickelson wasted little time on Monday charging to the top of the leaderboard of the event originally due for completion on 1 February when rain washed out the final two rounds and forced a postponement of a rescheduled 18-hole final round on 2 March.
The 28-year-old Mickelson finished with a 54-hole total of 14-under 202 for his second victory this year and 13th overall. He held off Tom Pernice Jnr by one stroke and Jim Furyk, Paul Azinger and JP Hayes by two shots.
Tom Watson, the second-round co-leader, carded a par 72 and finished in a three-way tie for ninth at 10-under 206. Vijay Singh, who captured the USPGA, withdrew following Sunday's win.Reuse content