Tom Jenkins carded a 2-under 70 to share second place at 11-under-par 205. He was joined there by Bob Gilder, who won two weeks ago at the Constellation Energy Classic. Craig Stadler, the 2004 champion, was one stroke further back at minus-10.
Irwin surely didn't look like he was going to make a run at the title early on Sunday. He played the first seven holes in 1 over with a bogey on the third at Prestonwood Country Club.
The 60-year-old got that stroke back with a 20-foot birdie putt on the par-3 eighth. Around the turn, Irwin caught fire. He dropped in a 7-foot birdie putt on the 10th.
Irwin birdied the par-5 12th and made it two straight with a birdie on 13. He sank another birdie putt on the 14th to move to minus-11. Irwin ran home an eagle putt from the back fringe at the par-5 17th to jump out in front at 13 under.
'When I made the turn, I didn't give it much thought that I'd win because I didn't play that well on the front nine,' said Irwin, who earned $285,000 for the win. 'The birdie on 10 kind of opened the floodgates and I started putting more aggressively. Of course, the eagle at 17 was the clincher.'
Jenkins parred his first five holes before dropping in a birdie putt on the par-4 sixth. The six-time winner on the Champions Tour stumbled to consecutive bogeys from the eighth to drop back to minus-8.
The 57-year-old parred the first five holes on the back nine. Jenkins birdied the par-4 15th, then closed with back-to-back birdies to share second place.
Gilder started the day at 10 under, but fell backwards with bogeys on the second and fifth. He quickly got those strokes back with a birdie on six and another on the seventh.
The eight-time winner on the Champions Tour stumbled to another bogey on the 10th, but came right back to birdie the 11th. Gilder birdied the 15th to get back to minus-11. He had a chance to get to 13 under and force a playoff with Irwin, but he could only par the final three holes to end two shots back.
'I felt pretty good out there today, but my iron play let me down and I needed to hit the irons well,' Gilder said. 'I had two three-putts early which really hurt. My iron play put me in the bad positions though.'
Danny Edwards finished alone in fifth place at 8-under-par 208. Bruce Lietzke, Gary McCord, Lonnie Nielsen and Bobby Wadkins were one stroke further back at minus-7. Eaks shared 10th place with James Mason at 6-under-par 210.