A second-half goal from Calvin Shand, his first at senior level, earned Peterhead their first league win of the season.
For long spells, the game looked to be heading for a draw until the former Cowdenbeath youngster scored the 63rd minute winner.
Dumbarton created the best chance of the first half after 14 minutes, defender Chris Gentile sending Andy Rodgers clear with a pass from midfield, but the striker's shot, with only home keeper Paul Mathers to beat, was too casual and went wide of the left- hand post.
Peterhead rarely threatened until the final 10 minutes of the first half,.Dougie Cameron and Graeme Sharp going close before a Keith Gibson free-kick was pushed clear for a corner by keeper Stephen Grindlay.
Rodgers had another great opportunity at the start of the second half, but mis-hit his shot beyond the far post.
Peterhead then proceeded to dominate, and scored what proved to be the winner after 63 minutes. Scott Michie had a shot cleared off the line. His second effort broke off a defender to Shand at the back post, and he headed in from three yards. .