Hawpe, who also homered in the Rockies' fifth win in seven games, hit a shot into the right-field gap that scored Seth Smith from first base.
Smith and Troy Tulowitzki also hit home runs for Colorado.
Huston Street (3-1) pitched a perfect ninth inning and earned the win.
Brooks Conrad homered, singled and tripled for Atlanta, driving in three runs.
Luis Valdez (0-1) took the loss in his first major league appearance. Valdez entered the game in the ninth and gave up a single to Smith and Hawpe's game-ending double.
Copyright 2009 by United Press International.