The Capitals (46-17-8) defeated the Tampa Bay Lightning 5-3 on Saturday after the New York Islanders lost to the Columbus Blue Jackets 3-2 in overtime.
Washington is in first place in the NHL, Eastern Conference and Metropolitan Division.
The Capitals, who won the Presidents' Trophy last season, have qualified for the playoffs the past three seasons and in nine of the past 10. Washington was eliminated in the Eastern Conference Second Round by the Pittsburgh Penguins in six games last season.