With Furyk nervously sitting on the stairs behind the green, Singh hit his 165-yard approach shot about 20 feet over the pin.
"I knew he had a pretty tough putt," Furyk said.
To Furyk's relief, Singh's bold putt ran 5 feet past the pin.
"I had my chances, but I couldn't get it going on the front nine," Singh said. "Jim played the front 4 or 5 under, so that's a big swing there. ... I had a chance on the last, but Jim played well. Anyone who shoots 7 under on the last day is deserving."
Furyk followed the hole-in-one with five straight pars, then holed a 5-foot birdie putt on the par-4 10th to reach 14 under and take a two-stroke lead over Mahan and Palmer. The 2003 U.S. Open champion moved three shots ahead on the par-5 11th, two-putting from 30 feet for a birdie.
After Mahan birdied the 11th to pull within two strokes, Furyk after stepping away three times to further examine his line rolled in a delicate 8-footer on the par-4 12th for his third straight birdie and a three-shot lead.
Singh and Mahan cut Furyk's lead to two, but he pulled three ahead again with an up-and-down birdie on the par-5 15th. Furyk also scrambled for key par saves on Nos. 8 and 14 both par 3s and the par-4 16th.
Furyk is the first player to successfully defend a title in the event since Jim Ferrier won in 1950 and 1951. Sam Snead (1940-41), Leo Diegel (1924-25; 1928-29) and J. Douglas Edgar (1919-20) also accomplished the feat.
Because of the tournament's new position on the PGA Tour schedule, Furyk probably would have taken the week off if he hadn't won last year. For most top players, the national championship wasn't a viable option because of its spot after the British Open and before the WGC-Bridgestone Invitational and PGA Championship. Furyk and No. 7 Singh were the only players in the top 35 in the field.
"I really appreciate all the support I had," Furyk told the fans during the during the trophy presentation on the 18th green. "It's been great coming to Canada the last two years. We'll see you next year."
Divots: Furyk earned $900,000. He opened with rounds of 69, 66 and 69. ... Stephen Ames was the top Canadian, closing with a 69 to tie for 27th at 7 under. He's a naturalized citizen from Trinidad and Tobago. Weir shot a 71 to tie for 34th at 5 under. "Today wasn't what I expected," Weir said. "I thought I was going to shoot a good score." ... A Canadian flag topped the flagstick on the 18th green.