Wadkins ended the championship at 14-under-par 274, one stroke clear of Jim Thorpe. Wadkins won for the second time this year and for the third time in his Champions Tour career.
Thorpe could have forced a playoff, but a bogey on the last left him at minus-13 after a closing 3-under 69.
Third-round leader Loren Roberts faltered in the final round for the second straight Sunday. Roberts set a USGA record with his 8-under 62 in the third round of the U.S. Senior Open last week, but a final-round, 3-over 73 dropped him into a share of eighth.
This week, Roberts used rounds of 67-64 on Friday and Saturday to lead by two shots entering the final round at TPC of Michigan. His lead was as big five strokes on Sunday, but two double-bogeys and a bogey on the back nine dropped him into a share of third at 12-under-par 276.
Roberts finished alongside Jay Haas (68), 1998 winner Gil Morgan (69) and Des Smyth (70).
The 51-year-old Roberts drained back-to-back birdies from the third to move to 16 under, four strokes clear of Dana Quigley and Morgan. He parred his next six holes before disaster struck.
Roberts found a hazard off the tee at the 12th and that led to a double-bogey, which dropped him into a share of the lead with Thorpe. After a three-putt bogey from over the green at 12, Roberts found another hazard on 14. That led to another double-bogey, which dropped him four back of the leaders.
Thorpe opened with seven straight pars. He then ran off three consecutive birdies from the eighth to get to 13 under. A birdie on the par-5 13th got him to minus-14.
Wadkins tripped to a bogey on the first, but he came right back to birdie two. He birdied the fifth to get to minus-11 before five straight pars. From there, Wadkins turned it on with his putter.
The 54-year-old birdied the 11th, then drained 30-footer for birdie on 12. At the par-5 13th, Wadkins' birdie got him to minus-14 and a share of the lead with Thorpe and Roberts.
Wadkins poured in a birdie putt on 14 from nearly 35 feet to take the lead. He came up short of the par-3 15th, but ran in a lengthy birdie effort from the fringe to go two up on Thorpe.
With a two-stroke cushion, Wadkins was starting to feel some pressure as he went for his first major title. He missed the green at 16 before two-putting for bogey.
Wadkins, one ahead of Thorpe, pitched his third to 4 feet at the 17th and tapped that in for birdie and a two-stroke lead with one to go.
Thorpe, playing one group ahead of Wadkins, got too aggressive at the 18th. Thinking he needed birdie to possibly tie Wadkins, Thorpe ended with a three-putt bogey to fall three behind.
'I knew I needed to make birdie there (at the last) and the second shot played very long into the wind,' Thorpe stated. 'The back nine played very, very hard. If I had known what Bobby was going to do, maybe I'd have played it a little different. Hindsight is 20/20, and unfortunately I three-putted for bogey.'
Wadkins made things interesting, though, when he drove into a hazard at the last. After taking his drop, his third came up short in a greenside bunker. Wadkins then blasted his fourth over the green into the rough.
Needing to get up and down to avoid a playoff, Wadkins' bogey chip hit the hole, but rolled eight feet past. No worries though. Wadkins drained that putt for double-bogey, which was good enough for the one-shot win.
'I played so perfect on the back side until the last hole. I knew I had a two-shot lead,' Wadkins admitted. 'I hadn't hit a bad tee shot all day. I was just trying to hit a hard drive down the left side of the fairway and not get blocked out by the tree.'
Smyth had five birdies and two bogeys over his first 16 holes to get to 13 under. He also had a chance to get to 14 under with a birdie at the last, but he knocked his approach over the green, then two-putted for a closing bogey to end in a share of third.
Brad Bryant, a two-time winner this season, closed with an even-par 72 to join Tom Purtzer in seventh place at 11-under-par 277. Tom Kite and Fuzzy Zoeller were one stroke further back at minus-10.
Fred Funk, playing in his second straight Champions Tour event, shared 11th place with Morris Hatalsky, 2004 champion Mark James, Dan Pohl, Don Pooley and Dana Quigley at 9-under-par 279.