Singh was joined in the playoff by Sergio Garcia, who led after each of the first three rounds and Jim Furyk. Garcia bogeyed the 17th hole of regulation to close a round of even-par 72, while Furyk birdied the 18th hole to cap a round of 6-under 66.
In the extra session, Garcia found the 18th green with his second shot after Furyk's second bounced over the putting surface. Singh, playing third, knocked his second to 40 feet.
Garcia was out of the playoff and with that tied the PGA Tour record for losing the biggest lead entering the final round. Garcia squandered a six-shot lead, which tied the mark of four others.
'I think I hung in there well. All the credit in the world to Vijay and Jim,' said Garcia. 'They played two very good rounds. But I played awesome the first eight holes. I should have been easily three- or four-under and I was one- under. It was tough. I'm disappointed, no doubt about it, but at the same time I'm happy about the way I performed all week.'
Both Singh and Furyk landed their second shots on the putting surface at the second playoff hole, No. 16. Each man two-putted for par and it was off to the 17th at Quail Hollow Club for the third extra hole.
Singh stuck his tee ball at the par-3 17th within 6 feet, putting the pressure on Furyk. However, the 2003 U.S. Open champion responded by dropping his tee shot 14 feet from the hole.
Furyk's putt slid by the left edge and the tournament looked like it was Singh's. However, the Fijian missed a hard-breaking putt and tapped in for par. Furyk rolled in his par putt and it was back to the 18th for the fourth extra hole.
Back on No. 18 for the fourth playoff hole, Singh found the right side of the fairway with his tee shot. Furyk then pulled his tee ball into a creek left of the fairway.
After taking a drop, Furyk pitched his third down the fairway from a thick lie in the rough. Singh looked to open the door for Furyk as he lost his second shot into a bunker right of the putting surface.
Furyk got an unlucky break as his fourth shot from 97 yards out hit the pin and spun some 50 feet away from the hole and in the rough.
Singh made sure the playoff would not go on. He blasted his bunker shot inside 2 feet and tapped in for par to win for the third time this year, two of which were playoff wins.
'You have to just go ahead and play it,' said Singh of the playoff. 'You shouldn't be disappointed that you could have lost. Of course you're going to be disappointed by not winning in regulation, but you just go ahead and play.
'Playing a playoff is like a coin toss. You have to go out there and play and hit the best shots you can. Straightaway it's match play and whoever gets 1-up that's it.'
Singh, a three-time major championship winner, played the front nine in 3-under with an eagle, two birdies and one bogey.
The 42-year-old caught fire on the back nine. Singh two-putted for birdie on the par-5 10th to get within one of Garcia. Singh, playing one group ahead of the Spaniard, birdied the 11th to join Garcia in the lead at 11-under.
Garcia came right back with a birdie of his own on the 11th to regain first. Singh rolled in a 5-foot birdie try on No. 12 to again tie Garcia at minus-12.
Singh made it four straight birdies as he drained a 14-foot birdie putt at 13 to take a one-stroke lead. His margin grew to two as Garcia bogeyed the 13th.
Garcia climbed back within one with a birdie on 14. Singh knocked his second shot over the green at the par-5 15th. He left his third shot short and walked away with a bogey. Garcia birdied the same hole to go from one down to one up.
Garcia knocked his tee shot in the water on the 17th. That led to a bogey and he slipped to minus-12 alongside Singh. Singh parred his final three holes to remain at 12-under. Garcia parred the last to end at 12-under.
'Obviously it was pretty exciting there at the end,' said Singh, who earned $1,080,000 for the win. 'You know, Sergio made it a little easier for us by bogeying 17. Even in the playoff, it was pretty tense. You can't miss a golf shot out there because the golf course will not yield at all. It was tough playing the finishing holes, but I played really solid today.'
Furyk, on the other hand, was chasing the leaders all day. He ran off four consecutive birdies from the fifth to jump to 10-under. Furyk, who turns 35 years of age on Thursday, tripped to a bogey on the ninth.
Around the turn, Furyk got within one of the leaders with birdies at 10 and 16. He then drained a 25-footer for birdie at the last to join the playoff. That was just the fourth birdie all day on the 18th.
'I played really well,' Furyk said. 'I hit the ball as well as I could have hoped for. I hit some really good putts out there; some went in, some didn't. Coming down the stretch, it didn't really look like I was going to have an opportunity to get back in the golf tournament and get in that playoff. You don't expect to birdie two of the last three on this golf course.'
Chris DiMarco also fired a 66 to finish alone in fourth at 8-under-par 280. Vaughn Taylor and Carlos Franco shared fifth place at minus-6.
Phil Mickelson made a huge run on Sunday. He was 9-under par for his round through 15 holes. Lefty faltered down the stretch with a double-bogey on 17 and a bogey on 18. He posted a 66 to share seventh place at 5-under-par 283 with Greg Owen.
Tiger Woods played the front nine at even-par. Around the turn, he collected an eagle at the 15th and a birdie at the last. However, after his round he was assessed a two-stroke penalty for moving a temporary immovable structure on the 10th hole. That dropped Woods from what would have been a share of ninth into a tie for 11th at 2-under-par 286 after a 1-under 71.