The 32-year-old center missed the past eight games with an upper-body injury.
"As of today, I'm good to go," Backstrom said Sunday. "I woke up and felt good. … Woke up. No pain."
Backstrom, who hasn't played since a 5-2 win against the Anaheim Ducks on Nov. 18, centered a line with Alex Ovechkin and Tom Wilson during practice on Sunday. He returned to practice with the Capitals on Dec. 2, but Sunday was the first time he took regular line rushes.
"It was good to see him out there in full practice," coach Todd Reirden said. "We did some drills specifically to prepare him for tomorrow, so he's good to go for tomorrow."
With Backstrom returning, the Capitals are expected to have their full lineup healthy for the first time this season. They began the season without defenseman Michal Kempny, who missed the first eight games while recovering from a torn hamstring, and have had various injuries throughout their first 31 games.
Despite that, Washington (22-4-5) leads the NHL with 49 points and has won six straight, including a sweep of its four-game road trip against the Detroit Red Wings, San Jose Sharks, Los Angeles Kings and Anaheim Ducks that concluded Friday.
"It's good," Backstrom said. "As of right now, we are playing good hockey and we are getting the points we needed so it is still early in the season, so you have to keep build, build and build. We are a team that is building for upcoming things. As everyone knows, you have to have a good regular season too, so we are just trying to build our game for what is coming."
Backstrom is seventh on the Capitals with 18 points (four goals, 14 assists) in 23 games.
