Two goals by Iain Russell continued Dumbarton's good start to the season in a scrappy encounter at Gayfield.
It was Arbroath who started the brighter and John Cusick went close from 18 yards after good work by Duncan McLean.
However, it was Dumbarton who took the lead shortly after when Gavin Swankie gave the ball away to Steven Bonar who played in Russell to score.
While Russell was calm in slotting home the opening goal, he blew a great chance to double Dumbarton's lead only eight minutes.
Robert Dunn flighted in a free-kick to the edge of the six yard box but the unmarked Russell headed wide with the goal at his mercy.
Arbroath steadily improved as the first half wore on, and were unlucky not to equalise on the stroke of half time. Swankie's low corner was met by Jamie Bishop but his effort went just over.
After the break Dumbarton regained control of the game thanks to some slack passing by the home side. On 66 minutes, Steven Cook saved Arbroath by clearing and Andrew Rodgers efforts off the line.
However, 20 minutes later Arbroath's shaky defence was breached again. Kevin McMullen failed to deal with a long ball and Iain Russell once again took full advantage.
Although his first effort on goal was saved by Neil Inglis, the striker fired home the rebound.
The second goal was no more than Dumbarton deserved and they will now be looking to maintain this good form throughout the season.