Adam Scott recorded back-to-back victories on the PGA Tour as Rory McIlory's challenge unravelled at the World Golf Championship at Doral.
The 35-year-old, who won the Honda Classic last week, began three shots adrift of McIlroy but closed with a three-under 69 to win on 12 under.
He holed a six-foot putt on the last to beat Bubba Watson (68) by one shot.
Northern Ireland's McIlroy had a two-over 74 to join England's Danny Willett (69) in a tie for third on 10 under.
Scott began his round with a birdie, but double bogeys on the third and fifth looked to have derailed his challenge as he fell six shots adrift of McIlroy, who opened with six pars.
However, six birdies in his next nine holes, as McIlroy dropped three shots, gave Scott a lead he did not relinquish.
"You have to push yourself so hard to beat the class of players that is out here right now," said Scott.
"So I can't believe I won back-to-back weeks. To win a world championship event is huge. I'm going to push hard the next few weeks."
Australia's Steven Bowditch, 32, recorded the worst ever score in a WGC event after a 12-over-par final round left him 37 over for the tournament.