Wideman finished his first career hat trick and sealed the win with a shot from the point with 1:19 left in the game.
Washington got even for its worst loss of the season with a good performance on the power play, which had been a weakness during the Capitals' recent woes.
Washington was 4 for 6 on the power play against Toronto, after going 3 for 51 in the previous 14 games. It was the first time this season the Capitals have scored more than two power-play goals.
Nicklas Backstrom also scored and had two assists for Washington. Phil Kessel
and Cody Franson
scored for the Maple Leafs, who defeated Washington 7-1 in Toronto the last time these teams met on Nov. 19.
The loss in Toronto marked perhaps the low point for Washington this season.
Four games later, the Capitals fired coach Bruce Boudreau and brought in Dale Hunter to try and turn around the team.
Washington lost three of the first four games under Hunter, but has now won two in a row.
The Capitals were scoreless on five power-play chances in the teams' first meeting, but Washington scored on its first three power-play opportunities Friday.
Washington's offence got off to a slow start. The Capitals didn't record their first shot on goal until nearly 12 minutes into the first period. The second shot came soon after, and Washington made it count.
Toronto's Jake Gardiner
was called for slashing at the 12-minute mark, and the Capitals scored 33 seconds later on Wideman's shot from the right circle.
Maple Leafs goalie James Reimer
was screened by Washington's Brooks Laich on the play, which gave the Capitals a 1-0 lead.
Wideman's second goal on a slap shot from the point came less than two minutes into the second period, and only 11 seconds after Toronto was called for too many men on the ice.
The Maple Leafs got on the board at 12:52 of the second period when Kessel poked in a loose puck that had gotten behind Capitals goaltender Tomas Vokoun for his 18th goal of the season.
Backstrom scored the Capitals' third power-play goal during a 5 on 3 at 18:50 in the second period, and Wideman had a hand in this one as well.
Wideman got the puck in the right circle, faked a shot and then passed to Backstrom who was in front of the net on the left side. The goal was Backstrom's 11th of the season.
Franson scored at 13:16 of the third period to cut the lead to 3-2. NOTES:
Washington D Roman Hamrlik (lower body) returned after missing four games. D Jeff Schultz was a healthy scratch. ... Toronto F Colby Armstrong
was activated from injured reserve and returned to the lineup after missing 23 games with an ankle sprain. The Maple Leafs assigned F Joe Colborne
to the Toronto Marlies of the American Hockey League to make room. ... F Clarke MacArthur
also played after sitting out a game with an upper-body injury.