Midfield star Alex Grace earned Dumbarton their first home win of the season but it was keeper John Hillcoat who kept them in the points as the home side clung on for a 1-0 victory.
After shading the early exchanges, Dumbarton should have gone in front after only four minutes but Gary McGlynn made a great save to deny Steven Bonar.
Just a minute later Steven Marwick blasted a thunderous shot off the post as Montrose battled back, and Hillcoat was the busier keeper in the first period denying new signing Andy Hutcheon and his strike partner Jerry O'Driscoll on several occasions.
As the momentum swayed back and forth, home striker Paddy Flannery hit the post before the Sons finally opened the scoring when Flannery turned provider with a clever back-heel that gave Grace a simple chance from 10-yards out.
Montrose rallied after the break in a bid to find an equaliser but Hillcoat was again in fine form, denying O'Driscoll and later substitute Mike McKenzie.