Even with a two-stroke penalty, Johnson won by one over Jason Dufner and got to slip on the plaid jacket Sunday for his first victory since also winning at Hogan's Alley two years ago.
"There's a number of adjectives I'm calling myself right now. And lucky would be the biggest one," Johnson said. "Blessed would be another one, humbled would be another one. It's an honor to put this jacket on once. ... I'm in shock I got it twice."
Johnson moved his original ball mark out of the line of Dufner's putt on the 18th green. But he never moved it back before his final 5-foot putt.
The penalty was assessed before he signed his scorecard, and Johnson's 12-under 268 total was enough to edge Dufner, who finally faltered and closed with a 74.
Johnson had already shared celebratory hugs and kisses with his two young sons and done a winner's television interview before caddie Damon Green, prompted by a rules official, asked the 2007 Masters champion if he had put his ball back in its original spot.
"First time it crossed my mind," Johnson said. "It's not going to be the last time."
The victory came 10 days after Green's 88-year old father died from stomach cancer. After Johnson's runner-up finish at The Players Championship two weeks ago, the caddie drove to Pensacola, Fla., to see his father. But Damon Green was ready to get back on the course this week.
"He wanted to be here, he felt like his dad wanted him to be here," Johnson about his caddie of 10 years. "I think he's the one that deserves this one more than I do. His courage and certainly his strength to get through last week and then work, and work well this week, to stay focused somehow. That's really commendable."
It is the eighth PGA Tour victory for Johnson, who won $1,152,000 even as his record streak of 15 consecutive under-par rounds at Colonial ended.
Tommy Gainey was a distant third at 7 under after a 67, a stroke better than Jim Furyk.
In what was essentially a match-play final round, Johnson took command at the 414-yard 15th hole. Dufner's approach hit the left side of that green then rolled into a ditch, leading to a triple bogey that put him four strokes back after Johnson's par.
Dufner's only two PGA Tour victories came in the previous four weeks, a stretch when he also got married.
After winning last week at the Byron Nelson Championship, he was trying to match Ben Hogan, his hero, as the only players to win both PGA Tour events in the Dallas-Fort Worth area in the same year. Hogan did it in 1946, when the tournaments weren't played in consecutive weeks.
"Pretty good run, today obviously a little disappointing to play that poorly and not kind of a chance there at the end," said Dufner, insisting fatigue didn't come into play. "I feel pretty good actually. ... I just played really poorly today."
There had already been four two-stroke swings between Dufner and Johnson before that fateful 15th hole.
Dufner drove into a fairway bunker before the shot that trickled over a ledge into the water. He then pitched his drop all the way over the green and missed a 4-foot putt for double bogey.
Johnson made par at the same hole where a day earlier his approach settled into a grassy clump only inches from going into that ditch. With his feet together to keep from falling over himself, Johnson's pitch from about 81 feet rolled only inches from the cup.
"I hit a terrible shot (Saturday), got lucky. Got a nice break," Johnson said. "He didn't hit a great shot today. But he got a bad break. I don't know how else to explain it other than the fact that it's golf."
Johnson had blown a two-stroke lead before going back ahead with his 9-foot birdie putt at the 445-yard 14th.
At the 616-yard 11th, a straight par 5, Johnson's drive hit a tree and ricocheted back into the middle of the fairway. He took advantage with an 18 1/2-foot birdie putt to get to 15 under.
Dufner wasn't as fortunate with his wayward drive, which settled under a tree. He had to punch a low shot around the branches before hitting his approach into a greenside bunker and two-putting from 23 feet for bogey.
But Dufner needed only one hole to get even again, with an 8-foot birdie at No. 12. Johnson hit his tee shot into a fairway bunker, then his first attempt out of there hit the lip and rebounded over and behind him before a bogey.
They were tied at 14 under going to the back nine after Dufner's double bogey at the 386-yard ninth hole, where his approach from 103 yards hit just short of the green and rolled back into the water.
After driving into a fairway bunker at the 382-yard second hole, Dufner three-putted from 28 feet for his first bogey on any of the first eight holes all week. Johnson made a 28-foot birdie putt to go in front by a stroke.
At No. 5, Dufner made an 8-footer for his third birdie of the week at the tight par 4 parallel to the Trinity River that is one of Colonial's toughest holes. Even after a frustrating tee shot into the rough at the sixth hole, Dufner regained the lead by rolling in a 34-foot birdie putt.
Johnson trailed by two strokes when his tee shot at the 188-yard eighth was way left before his short pitch shot missed the green and he bogeyed.
"What (Dufner) has done the last month is beyond impressive," Johnson said. "I kind of feel like I somewhat unseated a king to me because he has been on top for four weeks."
Divots: Hunter Mahan, No. 2 in the FedEx Cup standings behind Dufner, had three consecutive bogeys on the back nine and his only birdie in his round of 74 came on the last hole. He finished with a 282 total. ... Rickie Fowler, who in his previous two starts got his first PGA Tour win along with a runner-up finish at The Players Championship, shot a 69 and was in a group of five players tied for fifth at 275.
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