Anaheim's Mathieu Perreault potted a power-play goal to tie the tilt at 1:32 of the third, but Ducks forward Matt Beleskey went off for slashing at 2:36 and Ovechkin buried a one-timer from the low left circle just eight seconds into the ensuing man-advantage to put Washington on top for good.
Joel Ward and Troy Brouwer registered a goal apiece, while Jaroslav Halak stopped 43 shots for the Capitals, who have won three straight games to match Columbus with 76 points for the second wild card spot in the Eastern Conference.
Ben Lovejoy tallied Anaheim's other goal, while Jonas Hiller allowed three goals on 30 shots for the Ducks, who had a two-game win streak halted.
Ward opened the scoring with a tap-in from the crease just 2:11 in, but Anaheim answered just 59 seconds later when Lovejoy beat Halak short-side with a one-timer from the right point off a deft drop pass from Andrew Cogliano.
A power play late in the first helped Washington regain control, as Saku Koivu was sent off for interference at 19:29 of the opening frame.
With the Capitals controlling the puck in the Anaheim zone, Marcus Johansson rifled a shot from the right circle that Hiller turned aside, but Brouwer backhanded the rebound home for a 2-1 lead with 9.2 seconds on the clock.
The Caps killed off a 5-on-3 early in the second and then kept the Ducks off the board during Mike Green's hooking minor at 12:00, but a tripping penalty against Jay Beagle with 29 seconds left in the second came back to bite Washington early in the third.
The Ducks finally cashed in on the man-advantage 1:32 into the final frame, as Perreault ripped a wrister from the right circle that snuck between Halak's body and right arm to the tilt at 2-2.