Darron Stiles carded an even-par 72 to finish alone in second at 9-under-par 279 while Doug Barron, Arron Oberholser, Mark Wurtz and Casey Martin shared third at 8-under-par 280.
Dawson's victory was hard-fought at Kemper Lakes Golf Course, the site of the 1989 PGA Championship. Dawson began the day as part of a four-way tie for first but broke free thanks to solid play despite a miscue at the opening hole.
He bogeyed the par-4 first to fall one shot off the lead but responded with a birdie at the following hole. Dawson shifted the momentum into his favor again with a birdie at the fourth and added another pair of birdies starting at the seventh.
Dawson bogeyed the ninth to make the turn at minus 11 before a key par save at the 11th.
'I didn't think I hit it that poorly,' said Dawson. 'I was trying to hit a cut shot and it sort of got away from me. It was nearly out of bounds.'
His tee shot went right into the trees and stopped alongside a fence. Dawson could only advance the ball 10 feet with his third shot and he sent his fourth to the back of the green.
'That hole had disaster written all over it. I figured I was going to make bogey,' said Dawson.
The 38-year-old, who spent several seasons on the PGA Tour before injuries forced him into rehab, drained the 15-foot putt for par.
'That putt was more important than the score on that hole,' said Dawson. 'What a big momentum builder.'
Dawson carried that momentum onto the 13th where he rolled in a 30-footer for birdie. At the very next hole, Dawson hit his approach inside two feet for birdie to reach 13-under and open a three-shot edge over the rest of the field.
He bogeyed the 16th but his lead remained at three as his competitors faltered. Dawson then parred the last two holes for the win.
'When that last putt went in, I thought, 'Finally,'' said Dawson, who collected $81,000 for the win. 'The last tournament I actually won was a Golden Bear Tour event in 1998. A win out there only gets you to next week. A win out here gets you closer to the PGA Tour.'
A return to the PGA Tour is in sight for Dawson as he moved to fifth on the 2002 Buy.Com Tour money list. The top-15 money winners at season's end earn a trip to the big show.
Stiles got off to a good start with back-to-back birdies from the third but he ran into trouble with a bogey at the fifth. He added two more bogeys on his round to go along with one birdie and came up short in his quest for his second win of 2002.
Barron and Gene Sauers each held a share of the overnight lead but struggled Sunday. Barron had three bogeys and two birdies for a round of 73 while Sauers managed only two bogeys late in his round to finish alongside Barry Cheesman at 7-under-par 281.
Final results from the LaSalle Bank Open