Alexander Semin and Dainius Zubrus also scored for the Capitals (16-12-7), who led 3-0 after two periods and then held on for dear life in the third as Toronto pressed hard to tie the game.
But a loss is a loss and the Leafs enter the Christmas break on a three-game losing streak after seemingly turning around their season with a three-game win streak just before that. Overall, they're 3-9-1 in their last 12 games and fell to last place in the Northeast Division after wins by Boston and Ottawa on Saturday.
Mats Sundin had both goals for the Leafs (16-16-5), who were without front-line forwards Kyle Wellwood (groin), Alexei Ponikarovsky (shoulder) and Michael Peca (broken leg) - the latter out three to four months after undergoing surgery Saturday.
The Leafs resembled a team missing regulars in the first two periods, unable to mount much of an attack.
Ovechkin, now tied with Atlanta's Marian Hossa atop NHL goal scorers, broke a 0-0 tie with 7:59 to go in the second period on a Caps power play, pouncing on a rebound in front, shifting quickly from backhand to forehand and sending a wrist shot top corner on Andrew Raycroft's glove side. The Leafs goalie just moments before had stopped Semin on a breakaway.
Semin got on the board, however, less then two minutes later when he ripped a wrist shot from the top of the faceoff circle on a Caps power play, a sensational dart that beat Raycroft top corner on the glove side and even drew "ooohs" and "ahhhs" from the partisan Leafs crowd.
Zubrus made it 3-0 with 1:33 left in the second period, again on the power play, coming from behind the net with a nifty move and beating Raycroft with a wrist shot stick side.
The second period didn't end before Toronto's Darcy Tucker and Washington's Brian Sutherby got into a wild fight, Tucker trying to wake up his teammates.
Sundin energized a crowd of 19,488 at Air Canada Centre with a pair of goals just 14 seconds apart to make it a one-goal game. First Sundin scored on a penalty shot at 3:16 of the third period. Then he came roaring in on the ensuing faceoff and banged in a rebound at 3:30.
The ACC was suddenly as loud as its been all season long, Sundin's fist pump after the second goal was an unusual show of emotion for the 35-year-old Swede.
The crowd got more of their money's worth moments later when tough guys Donald Brashear of Washington and Wade Belak of Toronto squared off, a surprising draw that had the Leafs bench up and banging sticks on the boards in appreciation of Belak.
Seconds after the fight, Sundin had a chance to blow the roof of the ACC, but Kolzig stopped him on a breakaway.
The Leafs got handed a power play with 1:47 to go in the third period and pulled Raycroft for a two-man advantage, but still couldn't tie the game. Bryan McCabe's needless cross-checking penalty with five seconds left ended all chances.
Notes: Ponikarovsky is expected back in three weeks, while Wellwood is day to day ... Kris Newbury was called up from the AHL's Toronto Marlies in place of Peca and played in his first NHL game Saturday night. The native of Brampton, Ont., had 30 points (10-20) in 32 games with the Marlies this season. He was San Jose's fifth-round pick, 139th overall, in the 2002 NHL entry draft.