McIlroy had finished tied at the top of the leaderboard with Spaun following Sunday’s storm-hit final round after failing to hold on to a three-shot lead with five holes to play.
But after returning to the course on Monday in bright, breezy conditions, there was no sign of a repeat of the late stumble by McIlroy on Sunday that had allowed Spaun to force his way into the first playoff of his career.
McIlroy struck first on the opening playoff hole, the par-five 16th, crushing a 336-yard drive straight down the fairway before reaching the green in two.
Spaun meanwhile looked out of sorts from the get-go, finding the fairway rough off the tee before landing his second shot into the greenside bunker.
McIlroy failed to make his 33-foot eagle putt but calmly rolled in an awkward five-footer for birdie.
Spaun, whose recovery out of the bunker left him with a long, unsuccessful birdie putt, could only par.
After that early wobble, things got worse for Spaun at the par-three 17th island hole, with the American plunging his tee shot into the water behind the green.
Spaun then missed a long 10-foot putt for double bogey and eventually finished with a triple-bogey six.
While McIlroy missed his birdie chance and a 10-footer to save par, his bogey four still left him three shots clear heading to the 18th.
McIlroy’s tee shot on the last went well wide of the right fairway, but Spaun was unable to exert pressure, also going wide of the fairway.
Both players reached the green in three and missed their par putts. McIlroy coolly tapped in for bogey to seal victory.
McIlroy’s win marked the second title of the season for the Northern Irishman as he built towards the Masters in Augusta next month – the only major missing from his collection.
McIlroy said his early season form was a reward for the hard work he has put in over the years.
“I’ve worked really hard – I feel like I’m a way more complete player than I was a few years ago,” McIlroy told NBC. “I feel like I can play in all conditions and anything that comes my way. Really happy that I was able to get it done today.”
Spaun, meanwhile, was left reflecting on a disappointing outcome.
“It’s hard not to feel discouraged a little bit, but nothing but positives,” Spaun said. “Putting myself in contention and giving myself a chance to win in a playoff – if someone had told me that would happen at the start of the week I would totally have taken it.
“Hopefully I can just learn from this and get it done next time.”
