Fox pocketed $NZ1.2 million for the win.
He started this morning's final round in South Carolina three shots off the lead in a tie for fourth, and his bogey-free final round of 66 put him in contention for the title.
Fox, Canadian MacKenzie Hughes and American Harry Higgs finished regulation play tied at 15-under par.
The three went to a play-off hole, with Fox sinking a chip from just off the green to birdie. The other two missed their birdie chances to give Fox the victory.
"Honestly, I had a pretty similar line in regulation, I knew it didn't break much," Fox said afterwards.
"Both those guys had make-able chances so I knew I had to give it a go.
"When it landed, I go, 'This has got a chance,' and then about six to eight foot out, I thought 'this is in'."
Fox has had a mixed 2025 season so far, with his best result until now a tie for 15th. He had also missed four cuts.
"It's been a tough couple of seasons out here, just keeping my card last year and hadn't had a great start this year," he said.
"I also felt my game was good enough to compete with the best in the world, I got to show a little bit of it today and hopefully it kick starts things for me for the rest of the year."
The victory gives Fox a two-year exemption on the PGA Tour and entry to this week's PGA Championship, the second major of the year.
"I've played all of them (majors) the last two years and was gutted to have missed the Masters this year, so I knew there was one spot going this week and the only way to get it was to win, so I'm chuffed with that," he said.
"I love Quail Hollow (venue for PGA Championship), I might have a bit of a hangover driving to Quail, but I can live with that."
