The 28-year-old finished a shot ahead of Anirban Lahiri at TPC Sawgrass, going home with the winner’s check of $3.6 million.
Smith carded a six-under 66 to finish 13-under for the tournament and claim his second title of the season and fifth of his career.
When asked what he was going to do with such a large amount of money in the press conference afterwards, Smith hadn’t yet made up his mind.
“I really don’t — I don’t have an answer for that. It hasn’t sunk in,” he said with a smile.
“That’s a lot of money. I’m not sure what I’m going to do with it.”
The win held even more significance for Smith given who was within the crowd.
Amongst the fans watching Smith claim victory in Florida were his mother and sister, who he said he hadn’t seen in two-and-a-half years.
Smith, who lives in Florida, explained that “golf was second for these few weeks.”
“It’s really cool to have them here. My main priority really was just to hang out with them and golf was second for these few weeks.
“It’s nice to see them and nice to get a win for them.”
The tournament — one of the PGA Tour’s marquee events — was severely delayed due to inclement weather, with rain, darkness and lightning meaning it had to be finished on Monday rather the traditional Sunday final day.
When play resumed early on Monday morning, all 71 players left in the field had to complete their third rounds.
And after a quick turnaround, Smith began his final round strongly with a huge 38-foot birdie putt on the first hole.
He registered five birdies in his opening six holes, before three consecutive bogeys from the seventh hole weakened his grip on the lead.
But, under huge pressure, Smith reestablished his lead with four straight birdies to start the back nine, giving him a three-shot lead heading into the final hole.
Lahiri birdied the 17th behind Smith to cut the lead to two, while on the 18th, Smith hit his ball into the water as it looked like the title might be slipping away.
However, he managed to salvage bogey, leaving Lahiri needing a birdie to force a playoff, but the Indian golfer could only manage a par, cementing Smith’s victory.
The victory meant he became the fifth Australian to win the famous event, moving Smith up to sixth in golf’s world rankings.
“I felt as though one of these big ones was the next step for me,” Smith said. “I’ve knocked on the door a few times and I just felt like it was my time.
When asked about joining his countrymen in winning the tournament, Smith said: “Obviously, lots of Australians have won here, lots of great Australian golfers have won here, but the best that have ever lived have won here, as well.
“So it’s pretty cool to have the name on the same trophy as them.”