Dumbarton began both halfs by dominating play, but as manager Paul Martin confessed after the game their failing this season has been a lack of killer instinct when on top.
Iain Russell had two good chances to score in the first half, but he was to rue the misses as Peterhead went in front after 33 minutes.
Martin Wood was the creator cutting in from the left wing to set up Keith Gibson, who shot high into the net from 18 yards out.
Ten minutes after the restart the home side scored again. Graeme Sharp crossed low from the right wing and Wood swept the ball into the net at the back post after the Dumbarton defence failed to clear.
Substitute John Dillon sent over a corner from the left after 69 minutes and John Gemmell rose to head in from six yards to give the visitors some hope.
However three minutes later Sharp put his name on the scoresheet, squeezing the ball in at the near post after the visitors defence again failed to clear their lines.