Ernie Els rued his bad luck after a round of 67 was not quite enough to give him a first Green Jacket.
The big South African started the day at three under par and a run of two eagles and two birdies put him at the top of the leaderboard.
"I hit some really good shots and played the back nine as well as I ever
have," said Els.
"It was fun, but intense and it's hard to explain right now how I feel. I
just had a sense this was my year."
Els, who has won the Open and two US Opens, has now finished second, sixth, fifth, sixth and second at Augusta in the last five years.
After dropping shots at the third and fifth holes, Els produced some superb shots from around the green to ensure he did not make another bogey.
The world number three was practising his putting when he heard the roar that confirmed Mickelson had snatched victory from him.
Another three-time major winner, Nick Price of Zimbabwe, shot a round of 70 to finish the tournament on two under par.
Price, who shares the course record with Greg Norman, picked up three birdies on his inward nine to ensure a tie for sixth.
South Korean KJ Choi thrilled the galleries with a dazzling back nine which gave him third place on six under par.
Choi holed his second at the par four 11th for an eagle and put together a run of three birdies in four holes from the 13th onwards.
But he failed to make birdie at the par five 15th, which probably cost him a chance of putting more pressure on Mickelson and Els,
Fred Couples maintained his excellent Masters record with a final-round 70 and a two-under-par finish.
The American has now made the cut at Augusta on 20 consecutive occasions and he showed his mastery of the course with five birdies.
Compatriot Davis Love III shot 70 for a two-under-par finish and also carded five birdies in his round.
And 2000 Masters champion Vijay Singh shot a second successive 69 to join them on two under.
Singh had just squeaked into the weekend at four over, but two rounds of 69 guaranteed him a top-10 spot which will aid him in his pursuit of Tiger Woods' world number one spot.