Ogilvy went ahead at the first and never let Casey back in
Geoff Ogilvy beat Englishman Paul Casey 4&3 to win the WGC-Accenture Match Play Championship in Tuscon, Arizona.
Casey made a shaky start and was unable to get close enough to his Australian opponent to put any pressure on him.
Three up after 18 holes, Ogilvy, the 2006 champion and 2007 runner-up, forced home his advantage to take the $1.4m first prize.
In the third-place match, Englishman Ross Fisher was edged out by American Stewart Cink at the 18th to win 1up.
Despite having led for 79 of the 80 holes he had played in the tournament prior to Sunday, Casey made a nervous start to the 36-hole final at the Ritz-Carlton Golf Club.
He immediately went one behind when he missed from four feet for birdie at the first after Ogilvy had already holed from six feet.
Casey, chasing a first PGA Tour win of his career, missed another short putt on the severely undulating greens, this time at the sixth to go two down.
Ogilvy increased the pressure by winning the eighth and ninth to go four up before Casey halted the Australian's momentum in spectacular fashion, holing out at the par-four 10th hole with his second shot from 204 yards for an eagle.
The par-five 11th should have gone to Casey after Ogilvy found trouble after pulling his second shot into the jaws of a cactus.
But after a penalty drop, the Australian hit his fourth shot just short of the green before chipping in for an unlikely par.
Ogilvy had his lead cut at the par-five 13th when Casey holed his first birdie putt of the match, but the former got the upper hand at the par-three 16th.
Three-time Ryder Cup player Casey gave himself a boost heading into the lunch break when he won the 18th with a birdie three from 11 feet.
But Ogilvy would not give him an inch when play resumed.
The Englishman rolled in a birdie putt from 40 feet at the 22nd, but Ogilvy simply rolled in his own birdie putt from close range for a half.
At the 25th, Casey again laid down the gauntlet, firing in an iron to around 15 feet from the green only for Ogilvy to match it and cash in when his rival missed his birdie putt.
Casey's highlight was an incredible eagle at the 10th
Looking to become the first Englishman to win this event, Casey bogeyed the par-four ninth to lose the 27th hole and go six down, but an eagle at the 29th gave him a glimmer of hope.
When the 30th was halved, Ogilvy stepped up on the 31st knowing the win was in sight, but Casey birdied to push the match to another hole.
Ogilvy finally had a putt for victory on the 33rd hole - and the Australian's nerve did not let him down as he stroked home.
"I was out of the blocks fast this afternoon and made three birdies over the first eight holes and still lost two holes, so he played great golf," said Casey.
"I threw a lot at him but he didn't flinch. It was very impressive.
"I didn't have enough, simple as that. I have no excuses, he just played excellent golf all day."
Ogilvy, who had beaten Northern Irish sensation Rory McIlroy in the quarter-finals, said he was delighted with how he had played in Arizona.
"The whole weekend I played fantastic. I played two unbelievable players yesterday, Rory is going to be one of the best players in the world," said Ogilvy.
"Stewart Cink is very hard to beat in this tournament, always up there, and then Paul today, one of the best players in the world, a really great competitor head to head.
"I've been on the wrong end in this final, it's not a very nice feeling, but it's a very satisfying week to play well, I'm really happy with this."
In the consolation match, Cink took the $600,000 third-place prize in dramatic fashion when he holed with a stunning chip from the bunker on the 18th.
Fisher led the opening exchanges, leading until the ninth when a bogey let his American rival back in to level things up.
A birdie from Cink at the par-three 16th pulled the match level and ensured a tense run-in.
And he hit his third birdie in a row on the 18th to take the match, leaving Fisher in fourth and a cheque for $490,000.