Scott fought back from an ordinary opening round 71 in the Crowne Plaza Colonial Invitational tournament in Texas to storm home with a final round 66 and then score a play-off win over American Jason Dufner.
He sealed the triumph with a two metre birdie putt at the third extra hole while Dufner had to settled for par.
Scott, who was playing as the world’s top player for the first time since taking over from Tiger Woods on Monday, could have been in for a short stay with Swede Henrik Stenson breathing down his neck in Europe.
Stenson, the world No.3, had a chance of usurping the No.1 place and still had a chance after finishing tied for seventh earlier on Sunday in the European PGA Championship at Wentworth won by Rory McIlroy.
Based on that finish, Scott needed a top-13 place in the US to keep his place but two closing rounds of 66-66 and his subsequent play-off victory shut out the opposition.
Scott moved into a share of the lead for the first time in the last round of the Colonial when he sunk a 12 metre putt at the par four 14th hole for his seventh birdie of the day, bringing him level at nine under par with American David Toms.
While Toms dropped a shot at the 10th Dufner, the 2013 PGA champion, climbed to nine under with a curling six metre birdie putt at the last.
With Scott coming home in regulation figures, the tournament was sent into a play-off.
The duo shot pars at the first play-off hole – the par-four 18th – and both birdied the second. Scott then sunk a four metre birdie putt at the 17th, where Dufner could manage only par.
American Nicholas Thompson posted a 66 and Sweden’s Freddie Jacobson carded a 67 to share second on 272.
"This is a really special week for me – it was no matter what happened here," Scott said. "To kind of fight my way back into this tournament around this golf course, it’s a real honour to win here. It’s a beauty.
"There were some ups and downs for sure on the course, but it was great.
Scott becomes the first player on the PGA tour to have won all four Texas events – the Byron Nelson, Texas Open, Houston Open and now the Colonial.
"I was determined. I wanted to have a chance at this one, because I really wanted to win them all here in Texas," he said.
It was Scott’s 11th US Tour win and he becomes the fifth Australian winner this year on tour.
The consistent John Senden was the next best Australian, tied for fifth just two shots off the pace ahead of Marc Leishman (T21), Robert Allenby (T38), Matt Jones (T45) and Aaron Baddeley (T51). Victorian Geoff Ogilvy’s poor form this season continued with a missed cut.
On the Web.Com Tour, Australia’s Scott Gardiner made the most of his ineligibility for the Colonial event to finish runner-up at the Rex Hospital Open in Raleigh in North Carolina.
Gardiner will head back to the main tour with renewed confidence in two week.
He finished four shots behind the winner Byron Smith and tied for his runner-up position with Harold Varner.
Meanwhile, three months after his left thumb was injured while he won the Match Play Championship, and seven weeks after he aggravated the injury at the Masters, Jason Day will try to return to the PGA Tour at this week’s Memorial Tournament.
Tournament director Dan Sullivan said the world No.6 committed to the event last Thursday.
He said he had watched Day practising at Muirfield Village Golf Club, where he is a member. Sullivan said he had been told Day had improved and felt he could be competitive this week.
Day was injured in late February. He was forced to withdraw from a World Golf Championships event two weeks later and tied for 20th at the Masters in early April after receiving a cortisone injection.
But he reportedly re-injured the thumb when he hit a tree root during the third round, and the following week he withdrew from the tour event at Hilton Head Island, SC, after having the thumb put in a cast.
By: Robert Grant