The 28-year-old center was set to become an unrestricted free agent Friday, but opted to stay with the Capitals in the deal announced Tuesday.
Laich was acquired from Ottawa in the Peter Bondra trade in 2004 and has become a durable, two-way player. He has 100 career goals and 137 assists. He had 16 goals, 32 assists and a plus-14 rating last season.
Laich has played in all 82 regular season games in three of the last four seasons.