A flawless final round of 65 proved enough for Zach Johnson to drive off with the BMW Championship at a rain-soaked Conway Farms in Illinois.
The American made birdies at the 16th and 17th holes to finish on 16 under par, two shots clear of compatriot Nick Watney, who benefited in more ways than one from his 64 on Monday.
Overnight leader Jim Furyk had to settle for third place, a 71 on Monday meaning his three-year wait for a tournament victory goes on a little longer.
The win lifts Johnson up to fourth in the FedEx Cup standings going into the last event of the season at East Lake. If he can record back-to-back victories, the 37-year-old will collect the $10 million bonus on offer.
Furyk, who had led going into the final round of the PGA Championship only to be overtaken by Jason Dufner, had been forced to sit tight on his one-shot lead after rain prevented him from getting out on the course on Sunday.
A birdie at the par-fourth saw him double his advantage and he moved to 15 under when he picked up a further shot at the start of his back nine.
However, it all started to go wrong for the 43-year-old with a bogey at the 11th, leaving Johnson clear on his own at the summit after he had birdied the 12th.
Furyk then missed a par putt at the 16th to slip further back, and could only muster pars at the final two holes. It was a disappointing end to a tournament that had included him becoming the sixth man to card a 59 on the PGA Tour.
While Furyk was going downwards Watney was on the rise; his eight birdies helped him not only end as runner-up but also lifted him from 34th to 12th in the overall standings, meaning he now qualifies to play in Atlanta.
"I knew I needed to have a good week," he said. "The guys ahead of me were ahead of me for a reason. They've been playing well all year. Luckily for me I kind of pulled everything together."
Luke Donald will also be in the 30-man field after grabbing a share of fourth with Australian Jason Day and American pair Hunter Mahan and Steve Stricker.
The Englishman's final-day 66 carried him to 29th, though it was at the expense of Ryder Cup team-mate Lee Westwood as the man from Worksop slipped outside the necessary positions to make the Tour Championship.
Meanwhile, Tiger Woods carded a 71 to leave him on nine under for the tournament, the same score as American duo Jimmy Walker and Ryan Moore and Rory Sabbatini of South Africa.
Sergio Garcia of Spain finished on five under after a 72, with Englishman David Lynn a further stroke back.