He managed a final-round, 2-under 70 to finish at 12-under-par 204. That was good for a one-shot victory over Mark O'Meara (69) and Hale Irwin (68) at Ocean Hammock Golf Club.
In addition to collecting his first victory on the elder circuit, Fergus joined Ron Streck as the only players to win on the Champions Tour, PGA TOUR and Nationwide Tour.
'When your time comes, it just seems like it happens,' said Fergus, who pocketed $375,000 for the victory. 'I just hung around, hung around and it happened.'
Fergus began the final round with a one-shot lead and birdied the par-5 second. He found water at the fourth, but chipped in to save par, something he could not do at the sixth.
He atoned for that error with a birdie at the par-5 sixth and found himself among a group of leaders. Fergus moved clear of the pack at the par-5 10th when he holed out for an eagle from the bunker.
Now armed with a one-shot lead, Fergus had a good look at birdie at 11, but missed his 7-footer. He parred 12 and 13 and only needed a 7-iron to reach the par-5 14th green in two. Fergus missed his 15-foot eagle putt, but tapped in for birdie.
Fergus was 14 under par, but the difficulty of the finishing holes at Ocean Hammock caught up to almost everyone. Irwin and O'Meara got into the clubhouse at 11 under par, but Fergus' playing partners, Brad Bryant and Tom Purtzer, were still in the hunt.
Purtzer blinked first as he bogeyed the 15th. Fergus and Purtzer both bogeyed No. 16, but Fergus still held the lead by one at 13 under par. The par-3 17th hole became an important one as Purtzer was the only one of the three players that had any chance of birdie.
He missed from 22 feet, but Fergus had 75 feet for his birdie and he rapped his ball almost 10 feet past the cup. Bryant missed a 10-footer for par to fall two back, but Fergus had to hole his putt to keep that margin. He did and it turned out to be crucial.
'That was huge,' admitted Fergus, referring to his par save at the 17th. 'The last three or four holes are tough. When you're trying to win your first tournament, you let a few get away.'
Fergus let his tee shot get away at 18. His ball went right into a sandy area and he had no chance to reach the green with his second. Fergus laid up in the left rough, then hit his third to 13 feet.
Purtzer and Bryant both made bogey to fall to minus-10, but Fergus had to two- putt for the win. His par effort died left of the hole, but he tapped in for the bogey and one-shot victory.
'Up till then, I played solid all week,' said Fergus, referring to his closing stretch on Sunday. 'I can't complain about the way I played. Just lucky.'
Bryant and Purtzer finished with final-round, 1-under 71s and shared fourth place with Gil Morgan, who posted a 3-under 69. That trio came in at 10-under-par 206.
Fred Funk shot a 2-under 70 on Sunday and finished alone in eighth at minus-8.
David Eger fired an 8-under 64 and tied Raymond Floyd, who only managed an even-par 72, in eighth at 7-under-par 209. Bobby Wadkins (71) and Joe Ozaki (74) shared 10th at minus-6.