The hosts could not have got off to a better start when Tubbs headed home a free-kick by Mohamed Chemlal after just seven minutes.
Forest Green pushed for a second with Chemlal looking the man most likely to add to the score.
But Sutton scored an equaliser when Nick Bailey struck from the spot after Drissa Traore brought down Bedsente Gomis in the area.
Report supplied by the Press Association.
Match ends, Forest Green Rovers 1, Sutton United 1.
Second Half ends, Forest Green Rovers 1, Sutton United 1.
Roarie Deacon (Sutton United) is shown the yellow card.
Substitution, Sutton United. Maxime Biamou replaces Ross Stearn.
Substitution, Sutton United. Shaun Cooper replaces Gomis.
Nicky Bailey (Sutton United) is shown the yellow card.
Substitution, Forest Green Rovers. Rob Sinclair replaces Drissa Traoré.
Substitution, Sutton United. Chris Dickson replaces Dan Fitchett.
Substitution, Forest Green Rovers. Elliott Frear replaces Fabien Robert.
Goal!  Forest Green Rovers 1, Sutton United 1. Nicky Bailey (Sutton United) converts the penalty with a.
Kieffer Moore (Forest Green Rovers) is shown the yellow card.
Second Half begins Forest Green Rovers 1, Sutton United 0.
First Half ends, Forest Green Rovers 1, Sutton United 0.
Kieffer Moore (Forest Green Rovers) is shown the yellow card.
Ross Stearn (Sutton United) is shown the yellow card.
Goal!  Forest Green Rovers 1, Sutton United 0. Matt Tubbs (Forest Green Rovers).
First Half begins.
Lineups are announced and players are warming up.
Matt Tubbs' first goal for Forest Green Rovers was not enough to clinch a first victory of the season after a 1-1 draw with Sutton.