Scott will stay on top after a comeback victory at Hogan's Alley. He made a 7-foot birdie putt on the third hole of a playoff Sunday to beat Jason Dufner.
"It's so satisfying in so many ways to get it done," Scott said. "It's a good feeling, and maybe some validation."
Only days after officially overtaking injured Tiger Woods at No. 1, Scott bogeyed four of his first nine holes in the first round at Colonial. Midway through his final round, Scott had a double-bogey that dropped him three strokes off the lead.
"Maybe added a little pressure for myself, trying to play like a No. 1. But I think the important thing was I realized that didn't mean playing perfect, and I certainly didn't play perfect all week," Scott said. "But the way you come back and get it done, and I felt like I certainly played like one of the best players in the world out there on the back nine."
The Australian certainly did, with consecutive birdies in the playoff.
The major champions parred No. 18 to start the playoff before matching birdies at the 17th hole. Dufner, who won the PGA Championship last year, hit his approach pin high on 17 to 4½ feet, but 2013 Masters champ Scott drained a 14-foot birdie before Dufner putted.
Dufner, who made a 25-foot birdie putt on No. 18 in regulation, slid a 40-footer past when he and Scott played the 18th hole for the second time during the playoff. Scott then made the 7-footer for his 11th PGA Tour victory, 5½ weeks after the 33-year-old Scott got married.
"It's tough to beat him. He's a great player. It's tough to concentrate, he's so good looking, too," Dufner said. "I thought maybe I could sneak one in there on 17, but he topped me."
Scott and Dufner each shot 4-under 66 to finish at 9 under, the highest winning score at Colonial since 1999. They started the final round part of a seven-way tie for 11th place but only two strokes behind a quartet of leaders.
To stay No. 1 in the world ranking, Scott had to be in the top 13 at Colonial after Henrik Stenson finished in a five-way tie for seventh place in the BMW PGA Championship at Wentworth.
The win at Colonial, which came with $1,152,000 and a plaid jacket, made Scott the first player to win all four PGA Tour events in Texas. He is the 15th to win both the Byron Nelson Championship (2008) and the Colonial in the Dallas-Fort Worth area.
The 11th playoff in Colonial history was the first since 2009 and the longest since Jim Colbert beat Fuzzy Zoeller on the sixth extra hole in 1983.
Nicholas Thompson (66) and Freddie Jacobson (67) tied for third at 8 under.
David Toms, in the final group, led at 9 under when he made his turn. But he had three bogeys over the next five holes and finished with a 70.
Toms ended up 7 under with Brendon Todd (68), who last week got his first PGA Tour victory at the Nelson. Jimmy Walker, No. 1 in the FedEx Cup standings, shot a 70 and was tied for 10th at 6 under.
About 30 minutes after Dufner made his long birdie at No. 18 to get to 9 under, Scott made a closing par after just missing a 31-foot birdie chance that would have wrapped up the victory. It was just less than an hour later when the two went back to No. 18 to start the playoff.
Scott finished about the same time Toms was coming off a bogey at the par-3 13th that dropped him two strokes back.
Scott was 8 under after making a 6-footer at the 406-yard No. 6 hole, his fourth birdie in the round, and already had a bogey at the par-4 third when he three-putted from 24 feet. His only other three-putt at Colonial came from 17 feet at the ninth hole, dropping him to 6 under.
"I didn't want to let this one slip," Scott said. "As always, a bit of luck involved. And to come out on top is a really satisfying feeling, and hopefully keep No. 1 for at least another week."
Dufner, who also was second at Colonial two years ago, gave up a stroke when he missed a par putt from less than 3 feet at the straight 615-yard 11th hole. When his 12-foot birdie chance at the 440-yard 12th hole slid a half-foot past the cup, Dufner stood momentarily and stared at the ball before tapping in his par.
Scott caught up with consecutive birdies on those same holes, pitching to 9 feet at No. 11 before his approach at No. 12 to 4 feet.
Dufner had another near miss at No. 15, where another lengthy birdie chance slid inches by the hole. Scott got to 9 under with a 39-foot birdie putt at the 453-yard 14th hole.