In a game that went to form, goals in either half from Matt Ritchie and Ben Strevens - against his old club - were enough to earn the east Londoners bragging rights over their north London counterparts.
On-loan winger Ritchie opened the scoring on nine minutes with a well-directed header from Sam Saunders' excellent back-post cross.
Barnet worked hard to get themselves into the game, but it was the Daggers who looked the more dangerous.
Midfielder Solomon Taiwo tried his luck with a rasping drive from distance and then saw a glancing header from Saunders' whipped free-kick hit the inside of a post and run to safety.
Neal Bishop had the visitors' best chance of the half with a flashed low strike that was well saved by Tony Roberts
Dagenham's work ethic told after the break and the Bees were indebted to Lee Harrison's brilliant double save for keeping them in the game. First he parried Saunders' long-range effort and then reacted to turn away Ritchie's follow-up.
It was no matter for the hosts, who effectively tied the game up with a fortunate second just past the hour mark.
Paul Benson got in behind the Bees backline and pulled back for Strevens.
His poor first touch ran away from him, but, to show it was Dagenham's night, defender Joe Devera's clearance hit the forward and flew into the Bees net.
Ritchie should have put the game beyond doubt soon after, but with only Harrison to beat, he fired high and wide.
The Bees had a great chance to get themselves back in the game seconds later. Bishop put John O'Flynn through on goal, but the forward rushed his shot, firing wide of the target and ending the visitors; hopes of a comeback.
Benson had a late effort to put the icing on the cake for the Daggers, with a header that was cleared off the goal-line by Ashley Carew.