Alex Ovechkin scored the winning goal Thursday night as the Capitals defeated the Senators 2-1.
Evgeny Kuznetsov also scored for the Capitals as Braden Holtby picked up his 25th win of the season by stopping 25 shots.
Kyle Turris scored the lone Ottawa goal, and Robin Lehner made 27 saves.
"We had some great looks and the puck wouldn't go in for us," Senators captain Erik Karlsson said. "We need to score goals on the power play. That's one of the things that we've been struggling with."
Trailing 2-1 to start the third period, the Senators did their best to score the equalizer but couldn't find a way to beat Holtby.
"We got some good blocks from guys and some really good reads when they tried to go through the box with some seam passes," Washington's Brooks Orpik said. "Thought we were real sharp on it."
Thursday's game was a milestone for defenseman Chris Phillips, who set the franchise record by playing in his 1,179th game to surpass Daniel Alfredsson.
Alfredsson and former teammate Wade Redden were on hand for the occasion.
"It was a great day, a great couple of days leading up to it," Phillips said. "It would have definitely been a little sweeter with a victory tonight."
There was little excitement for the 16,543 on hand at Canadian Tire Centre in a scoreless first period. But Ovechkin made an impact early in the second as he drove Karlsson into the boards.
Ottawa took exception to the play and it resulted in Bobby Ryan and Ovechkin each taking roughing minors.
Turris opened the scoring midway through the second as Ottawa was rewarded for some solid work down low. Turris took a pass from Mark Stone and beat Holtby with a shot under the crossbar. It was Turris' first goal since Jan. 4.
The lead was short-lived as the Capitals scored two unanswered goals 49 seconds apart. Kuznetsov tied the game by putting home a rebound, and soon after Ovechkin hit the puck out of midair to beat Lehner.
"It's such a fine line between good teams and average teams in this league and it's just how consistent can you do things every shift, every game," Lehner said. "We're not doing it every shift so small details are hurting us."
NOTES: D Mark Borowiecki and D Patrick Wiercioch were healthy scratches. G Craig Anderson and RW Alex Chiasson (lower body) are day to day for the Senators. ... C Michael Latta, LW Aaron Volpatti and D Cameron Schilling were healthy scratches for Washington.