A five iron to four feet for birdie on the closing hole gave the 28-year-old European Ryder Cup star a two-stroke victory over Australian Geoff Ogilvy and ended a year-long wait to join the game’s elite.
Finishing second in the Players Championship and third in the Masters last spring helped Donald to 11th in the world rankings, but only now has he been able to take the extra step.
To do it with a win - and this time a “proper” win - was what meant most to the High Wycombe player.
Donald has lifted two other titles in America, but the first in 2002 came when the final round was washed out and the second in last December’s Target World Challenge was not an official US Tour event.
“Obviously I’m very excited right now,” he said as he celebrated a title worth nearly £620,000 (€898,000) with his brother and caddie Christian.
“Any time you win on the PGA Tour it’s a tremendous feat - and any time you finish with a birdie like that and a great shot it means a lot to a golfer. It’s nice to be back in the winner’s circle on this tour again after a four-year break.”
Donald, the joint overnight leader with Billy Mayfair, got out in front on his own early on, but three-putting the long sixth for par, then the seventh for bogey and missing from under three feet at the 10th to drop another stroke left him looking shaky and with ground to make up.
His response was brilliant. He made birdie putts of eight and 25 feet at the 13th and 14th, saved par from 18 feet at the 16th and then, needing a par on the last, settled the issue with arguably his best shot of the week.
“I don’t think I got ahead of myself. I didn’t look at the leaderboards until I saw one on 14,” he said.
“I was just determined to play my own game today and not worry about what anyone else was doing. I thought that if I could play Luke Donald golf it might be good enough.”
Donald is now up to fourth in the Ryder Cup race and has no doubt that his debut in Detroit two years ago helped him succeed Padraig Harrington as champion at Mirasol in Palm Beach Gardens.
“I think anything like that helps. The Ryder Cup was some of the most pressure I had ever felt and any time you can play in that pressure and experience it and come out on the other side it’s good for you,” he added. “You definitely draw off that kind of experience when the pressure is on.
“Do I think I can win majors? Absolutely - I think I have a great game for majors,” said the English golfer. I’m very steady and that’s the main reason why I think if I keep playing the way I’m playing, there’s no reason why I can’t strive to be the best player in the world.
“The British media are always looking for that next star to come up and be a great, what’s the word, icon, for England or whatever.
“I don’t really pay too much attention. I’m just trying to go out there and do the best I can. I feel like I’m on the right track to meet my goals and keep improving.”
Fellow Englishman Greg Owen finished 13th and Harrington 16th - disappointing for the Dubliner after he was joint third at the halfway point, but not as disappointing as 41st was for Ian Poulter or 55th for Lee Westwood.
Poulter is left with just two more chances - this week’s Bay Hill Invitational in Orlando and then the Players Championship at Sawgrass - to climb into the world’s top 50 and guarantee a place in the Masters.
Westwood is guaranteed that, but was left to reflect on back-to-back 77s after he shared seventh spot with Donald going into the third round.