Smyth's win came on the same day that fellow Irishman Padraig Harrington was victorious at The Honda Classic on the PGA Tour. Smyth becomes the second Irishman to win on the Champions Tour, joining Christy O'Connor, Jr.
'He's done great things already, but this is a big step for him to win on the PGA Tour,' said Smyth of Harrington. 'We have a great golfing tradition in Ireland. It's a great day to be Irish.'
D.A. Weibring carded an even-par 72 in the final round and was joined in second place at minus-4 by Mark McNulty. McNulty closed with a 2-over 74.
Craig Stadler got within one stroke of the lead during the final round, but stumbled to a pair of bogeys on the back nine. He was joined in a tie for fourth place by Gary McCord, who shot a 1-over 73 on Sunday.
Smyth, who turned 52-years-old Saturday, opened with a birdie at the par-5 first to get to 2 under. After five straight pars, he drained a 15-foot birdie putt at the par-3 seventh at Valencia Country Club.
The Irishman stumbled to a bogey at the eighth. Smyth came right back with a birdie at the ninth to make the turn at minus-2.
Smyth got hot on the back nine. He drained a birdie try from 4 feet out at the 12th. The 19-time winner worldwide made it two straight as his 3-foot birdie putt at 13 fell into the cup.
Smyth moved into the lead at minus-6 with a two-putt birdie at the 15th. He tripped to a three-putt bogey at the next, but parred his final two holes to come in at minus-5.
'I feel I stole it today,' said Smyth, who earned $232,500 for the win. 'The win is important for me. I thought I'd need a 66 today. I didn't think a 68 would be good enough.'
Weibring got to minus-5 as he birdied the opening hole. The two-time winner on the Champions Tour stumbled to a bogey at the sixth. He ran off seven straight pars around the turn.
The 51-year-old got back to minus-5 with a 5-foot birdie putt on the par-3 14th. Weibring had a chance to force a playoff, but bogeyed the par-4 17th to finish one back.
McNulty, who began the round in second place, fell off the pace quickly as he bogeyed the first and second. The Zimbabwean bounced back with a birdie at the fifth.
The three-time winner last year faltered to another bogey at the sixth. McNulty got one stroke back with a birdie at the par-4 eighth.
Around the turn, McNulty stumbled to bogeys at 11 and 14. He got back to minus-4 with a birdie at the par-5 15th to move back to 4 under. He parred out to share second.
Keith Fergus, the second-round leader, struggled to a final-round, 5-over 77. He was joined in sixth place at 2-under-par 214 by Mike Reid. Brad Bryant and Tom McKnight were one stroke further back at minus-1.