Dungannon dug deep to claim their second win of the AIB League campaign, coming under late pressure from Dolphin at Stevenson Park.
Barry Keeshan kicked Dolphin's only points of the first half as they trailed 17-3 at the interval.
Scrum half James Bates (23 minutes) and winger John McGuckin (33) both crossed for Dungannon tries.
Centre Paul Magee raced clear to touch down for the hosts after the break, but a Dave Ryan try and two more Keeshan penalties saw Dolphin rescue a bonus point.
Scorers:
Dungannon: Tries: James Bates, John McGuckin, Paul Magee; Cons: John McGuckin 2; Pen: John McGuckin
Dolphin: Try: Dave Ryan; Con: Barry Keeshan; Pens: Barry Keeshan 3
