'Today was a big step for me in trying to get through the forest for me in coming back,' said Irwin, who has been nursing an ailing back. 'From a timing aspect the win was fantastic.'
Gil Morgan, who held the lead after each of the first two rounds, saw his streak of rounds at par or better end with a 73 that featured a bogey on the closing hole. Morgan was joined by Gary Koch in a tie for second at 10-under-par 206.
Irwin came into the final round at Savannah Harbor Golf Resort and Spa trailing Morgan by a single shot but used a strong front nine to assume control of the tournament.
After he bogeyed the par-3 third, Irwin ran off four birdies over his next six holes to make the turn at 13 under par with a three-shot edge over his closest competitors.
'I didn't have any great expectations coming in here after four weeks off,' said Irwin.
The back nine was a different story for Irwin, however, and the all-time wins leader on the Champions Tour dropped a shot at the par-4 12th. Irwin was unlucky with a bad bounce off the green at the par-4 16th and he was unable to get up and down resulting in another bogey.
Meanwhile Morgan, who had trouble early in the round with back-to-back bogeys from the third, battled back with birdies at the 11th and the 14th to join Irwin at 11-under.
'I didn't play very well today,' said Morgan. 'If I'd made some putts it would have given me some cushion.'
Irwin kept on playing for par down the stretch and missed the green off the tee at the par-3 17th. He chipped to five feet and converted the par putt before heading to the 18th tee with tied with Morgan.
Morgan found trouble off the tee and sent his drive into a fairway bunker at the last. Irwin was in much better shape and knocked his second shot on the putting surface within 18 feet of the cup.
'I hit a good driver at 18,' said Irwin, who earned $364,000 for the win. 'It was sort of like old times out there with Gil and I.'
Irwin's birdie try missed but Morgan could do no better than a bogey. Irwin then tapped in for par and his first win of the 2004 season.
Don Pooley posted a 70 to join Craig Stadler in a tie for fourth at 9-under-par 207. Bruce Fleisher, Larry Nelson and Tom Purtzer followed at 8-under-par 208.
Dave Barr, who played in the final group with Irwin and Morgan, struggled to a 75 to finish at 7-under-par 209 along with Dana Quigley, John Jacobs, Andy Bean, Wayne Levi and Ed Fiori.