Atlanta Thrashers left wing Brad Larsen, center, vies for the puck against Washington Capitals center Brian Sutherby (16) during the first period of an NHL hockey game, Monday in Atlanta. (AP/Gregory Smith)
Slava Kozlov and Ilya Kovalchuk also scored for the Thrashers, who moved two points ahead of Tampa Bay in the division race. Kari Lehtonen stopped 31 shots.
Washington dropped its eighth straight and fell to 2-16 in road games since Dec. 26.
Alexander Ovechkin scored two goals for the Capitals, giving him seven goals and six assists in seven games against Atlanta this season. In 15 career games against the Thrashers, Ovechkin has 12 goals and 14 assists.
Ovechkin's power-play goal off the skate of Atlanta's Andy Sutton less than two minutes into the third period cut the deficit to 3-2. Kovalchuk answered with his 37th goal midway through the period.
Ovechkin's first goal of the game in the second period was his 40th of the season. The second-year star is the fourth player in Capitals history with more than one 40-goal season.
After Kozlov's goal gave Atlanta a 1-0 lead midway through the opening period, Boulton set up the play of the game.
Boulton stopped a possible breakaway for the Capitals with a steal and then passed the puck to Holik, who had to lunge forward to gather it. While sliding toward the net on his chest, Holik managed to push the puck past goalie Brent Johnson for a 2-0 lead at 16:51.
Ovechkin's first goal cut Atlanta's lead to 2-1, but Tkachuk answered with his 24th goal of the season. It was his fourth since his trade to the Thrashers from St. Louis on Feb. 25.
With Atlanta leading 3-1, Washington pulled Johnson in favour of Frederic Cassivi. Johnson, who stopped 12 of 15 shots, appeared to be injured when diving for Tkachuk's goal at 14:30 of the second period. Johnson lay face down on the ice for about a minute before struggling to his feet.
There was no immediate injury report.
Notes: Marian Hossa's assist on Kozlov's goal gave him points in 11 straight games, extending his Thrashers record. He has seven goals and 11 assists in the stretch. . . . Atlanta improved to 5-0-2 against Washington this season. . . . The Thrashers, who had a five-game winning streak snapped with a loss to Florida on Saturday, have won six of seven.