Anwar Uddin's first-half header was enough to claim three points for Dagenham at Forest Green.
The defender's goal came in the last 10 minutes of the first period as he got on the end of Sam Sloma's corner to nod in from the centre of the box.
Forest Green had a few good chances missed in the first half with Allan Russell and Alex Meechan both denied.
The home side came close to scoring an equaliser in the second half as new signing Russell shot over the bar.
Forest Green: Williams, Lawless, Butler, Edwards (Preece 31), Nicholson, Meechan (Beesley 68), Clist, Pitman, Afful, Russell (Zarczynski 80), Griffin.
Subs Not Used: Brough, Harrison.
Dag & Red: Roberts, Olayle (Atieno 35), Uddin, Leberl, Griffiths, Saunders, Southam, Rainford, Sloma, Benson, Akurang, Atieno (Batt 90).
Subs Not Used: Mackail-Smith, Lettejallow, Hogan.
Booked: Olayle, Atieno.
Goals: Uddin 37.
Ref: A Watts (England).