McIlroy surged past Rickie Fowler and held off another American Collin Morikawa to win by one shot at The Summit Club.

Former World No.1 Scott started the final round three shots behind Fowler, who was seeking his first victory in almost three barren years, with Smith a further two strokes back.

Scott finished tied for fifth at 21-under, four shots off McIlroy after a three-under 69, wrapping up his final round with two birdies.

Unable to make the most of some other putting opportunities, his sole birdie on the front nine came at the par-five third.

"It is a big carrot. I didn't know it would be this week." - Rory McIlroy on his 20th PGA Tour win.

Smith, meanwhile, finished in a share of ninth a shot behind Scott.

He managed six birdies but his score was dented by bogeys at the par-4 fourth and par-3 11th to sign for a 68.

A day after a sizzling 10-under 62 put him right in contention, McIlroy teed off for the final round in second place but seized control with a 35-foot eagle putt from just off the green on the par-five 14th.

RIGHT: Adam Scott was the best of the Aussies in a share of fifth despite struggling with the putter on Sunday. PHOTO: Alex Goodlett/Getty Images for CJ Cup @ Summit.

He then played mistake-free down the stretch for a six-under 66 to get to 25-under 263.

Second spot was taken by Morikawa, a member at The Summit Club, who shot 29 on the front nine to get in the mix and closed with an eagle for a 62.

Fowler never got going on Sunday with a pair of three-putts in a round of 71 curtailing his hopes as he shared third with half-way leader Keith Mitchell 67 at 22-under par.

McIlroy is the 39th player to win at least 20 times on the PGA Tour, and it's his fifth straight season with at least one tournament victory.

"It is a big carrot," McIlroy said of the 20 wins.

"I didn't know it would be this week."

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It was similar to his first win on the PGA Tour in 2010 at Quail Hollow, when he was also nine shots behind going into the weekend and closed with rounds of 66-62 to win.

Of the other Australians Marc Leishman had a final round eight-under 64 to finish tied for 38th along with Matt Jones, who signed for a 68.

Jason Day finished with a flourish with a round of 65, including an eagle on the par-five 15th, and was in a group that shared 64th with Cam Davis (68).