Wadkins shot a final-round 4-under-par 68 to better Allen Doyle (69) and Larry Nelson (69) by one shot in the Lightpath Long Island Classic.
'I know the reason I'm out here,' said Wadkins, who earned $255,000. 'I just want to get my share after 27 years.'
Wadkins becomes the 10th player to win in his Senior debut, and the first since his brother, Lanny, did so last year.
'I've set this goal for a year,' Wadkins said. 'Lanny told me I was capable of winning out here.'
He is the youngest winner in tour history at 50 years, 9 days. Gil Morgan was 50-years, 10-days old when he won his first event in 1996.
Jay Sigel led by three shots entering the final round, and threatened to run away with the event early. Sigel, winless since 1998, birdied holes 3-5, but double bogeyed the par-4 9th and made four bogeys on the back nine for a round of 74. He tied Walter Hall (69) for fourth place.
Wadkins started his professional career on the PGA Tour in 1975. He finished runner-up seven times, never claiming victory in 712 PGA Tour starts and in 65 on the Buy.Com Tour.
However, Wadkins did win the 1978 European Open and the 1979 and 86 Dunlop Phoenix titles on the Japanese Tour.
Having turned 50 on July 26, Wadkins accepted a sponsors invitation into this weeks tournament in Jericho, NY.
He opened in 65 at the Meadow Brook Club to earn a share of the lead, and then stayed in contention with a second-round 69.
Sunday, Wadkins double bogeyed the par-4 2nd, but responded with a double eagle on the very next hole.
Wadkins holed a pitching wedge from 135 yards on the 478-yard par-5 3rd.
After parring his final six holes on the front side, Wadkins birdied the par-5 10th and tied for the lead by making a 20-foot downhill putt for birdie on the par-4 16th.
He then took sole possession of first place at 14-under by sinking a 10-footer on the closing 172-yard par-3.
Nelson had a chance to tie Wadkins on the final hole, but missed his birdie putt from 25 feet.
Full-field scores from the Lightpath Long Island Classic