The Senators have the fewest number of wins (22) in the Eastern Conference but they added to the woes of the Thrashers, who are slumping out of playoff contention. Atlanta has lost 14 of its last 17 games and, after looking to be a certain playoff team, has dropped to 11th place in the Eastern Conference.
Ottawa took the lead just 2:56 into the game on the first career NHL goal for Colin Greening, who put a wrist shot past Chris Mason in his 12th game for the Senators.
Bobby Butler added to the Ottawa lead 60 seconds into the third period but Dustin Byfuglien brought Atlanta back within one less than 6 minutes later.
Nick Foligno again boosted the Ottawa advantage to two goals with 8:39 to play by tipping in a shot from Zack Smith.
Anderson had lost three of his previous four starts. Mason stopped 24-of-27 shots to take the loss.