Douglas had a pair of second-half touchdown runs - including a 65-yarder - that gave the Dukes (6-3, 3-1 Northeast) a three-score cushion.
Wagner (0-8, 0-3) led early, as a 13-play, 75-yard first-quarter drive culminated in Alex Thomson's 6-yard scoring toss to Lloyd Smith. Midway through the second, Thomson was picked off by Christian Kuntz in Wagner territory, and five plays later Douglas pounded it in from the 2 to tie it at 7.
The Seahawks went on another long drive, but settled for Bryan Maley's 42-yard field goal. Duquesne responded again, as Dillon Buechel connected with Chris King on a 28-yard touchdown pass, and led 14-10 at halftime.
Buechel was 10-of-24 for 121 yards and two touchdowns passes, including a 15-yarder to Wayne Capers Jr with 54 seconds left.