An early goal put Darlington in the driving seat after only five minutes when striker Liam Hatch rose to power in a close-range header from Franz Burgmeier's corner - his third goal of the campaign.
Dagenham's early response came from Matt Ritchie who headed wide from a good position inside the area a minute later.
In an open game, Darlington striker Billy Clarke saw his shot turned away by Daggers keeper Tony Roberts after ten minutes but the visitors should have equalised when Mark Nwokeji connected with an excellent right-wing cross from Danny Foster, but sent his effort wide from inside the six-yard box.
Home striker Hatch used his strength to good effect when turning his man on the edge of the area in the 23rd minute to fire straight at Roberts.
In the second half Darlington increased their lead after more great work from Hatch.
The striker kept possession and waited for midfielder Jason Kennedy who raced into the area before rounding Roberts and rolling the ball into the empty net.
Dagenham went further behind five minutes later and again it was that man Hatch who connected with a Neil Austin free-kick to turn the ball over Roberts from close range.
Darlington could have won the game by a greater margin, a 63rd-minute miss from Liechtenstein international Burgmeier and another Hatch header that drifted inches wide sparing keeper Roberts further misery.
The introduction of substitute Jon Nurse perked up the visitors and, in the 75th minute, Darlington keeper Simon Brown was called into action for the first time.
Nurse dribbled into the area and Brown did well to get down and turn the substitute's shot away. The loose ball was turned goalwards by Ben Strevens and Brown stuck out a boot to turn the shot around the post.