Englishman Hatton, 28, showed nerves of steel in difficult conditions over the last seven holes for a two-over-par 74 in the final round to hold off the challenge of Australia’s Marc Leishman.
Hatton was playing in only his second event since undergoing wrist surgery at the end of last year.
South Korea’s Sungjae Im finished a further shot back in third place, while world number one Rory McIlroy, who started the day joint second, tied for fifth after a 76.
Bryson DeChambeau carded a one-under final round to claim fourth place, while fellow Americans Keith Mitchell and Joel Dahmen also shot 71s to finish alongside McIlroy and New Zealand’s Danny Lee.
Hatton won his fourth European Tour title in a six-man play-off in the Turkish Airlines Open in November and shortly after playing in the season-ending event in Dubai a fortnight later had an operation on his wrist.
He held a two-shot lead going into the final round at Bay Hill and overcame a disappointing start after bogeying at the first and fifth holes with birdies at the seventh and eight.
Hatton then double-bogeyed the 11th, but with the pressure on he made par on each of the last seven holes to claim victory.
England’s Matthew Fitzpatrick produced the round of the day, shooting a three-under 69, which included five birdies and a double-bogey at the 17th, to climb 27 places and finish tied for ninth.
Hatton believes his temperament survived a major-style test after claiming his first PGA Tour title.
Only four players finished under par and Hatton’s fellow Englishman Matt Fitzpatrick was the only player to break 70 over the weekend with a closing 69.
Such conditions posed a serious test to Hatton’s famous temper but the 28-year-old kept his emotions in check even after a double bogey on the 11th, closing with seven straight pars to earn a valuable three-year exemption on the PGA Tour.
“It was so tough and obviously everyone’s dropping shots quite easily,” Hatton said in his post-round press conference. “And after the double on 11, which was pretty tough to take, I feel like I could easily have blown up after that, and managed to kind of keep my head a little bit, although I did get a bit frustrated.
“That’s always going to happen with me and as long as it’s not kind of keeping on over to the next shot, then I’ll be okay. And I’m just happy that I’ve managed myself well enough this week to be sitting here.
“I think players kind of would look back at this week and say it’s nice to play something different. Most weeks it’s not target golf, but the scores are super low.
“And this ended up sort of feeling like a major (championship) with the set-up and how firm the greens were and it was hard to hit it close. I don’t think there was even a handful of guys that were under par for the weekend.”
“Coming into this week I didn’t have any exemptions, so when the season starts you are kind of just playing to keep your status for the following year,” Hatton added.
“Obviously I’m trying to juggle both tours, which is never easy and I’m normally playing around 16, 17 events, so that makes things certainly a little bit tougher to try and keep your status over here. A three-year exemption is amazing.” PA