Chris Harrington and Kris Newbury scored for the Marlies (10-14-2-2), who have dropped two straight games and five of their last six.
Andrew Ebbett, with two, Danny Bois and Arttu Luttinen had the goals for Binghamton (9-15-1-2), which won its second straight.
Playing in front of an announced crowd of 3,479, the Marlies were first on the scoreboard when Harrington took a nice feed from Colin Murphy and beat Senators goalie Jeff Glass for a power play goal at 11:04 of the opening period.
Binghamton took a penalty with less than 28 seconds left in the first, and the Marlies made them pay for it on Newbury's power play marker at 1:32 of the second.
Ebbett cut Toronto's lead in half with his eighth of the year at 12:39 of the second.
Although the Marlies outshot Binghamton 16-7 in the second, they were unable to add to their lead. Bois tied the score with a power play goal at 6:40 of the third period, and Luttinen put Binghamton in front at 11:28 with a soft goal on Marlies netminder Justin Pogge.
Ebbett added an empty net goal with 46 seconds left in regulation.
Glass (4-8-1) made 36 saves in the win, while Pgge stopped 19 shots and fell to 3-9-0 on the season.
Notes: Fan balloting for the 2007 AHL all-star game kicks off Monday on the league's official website (www.theahl.com). Voting will decide both starting rosters for the Canadian team and the World team, who will face off when the game takes place at Toronto's Ricoh Coliseum Jan. 29. Fans may cast ballots until 11:59 p.m. on Jan. 7 . . . Binghamton's Bois took four penalties - all for different infractions - during the game.