The deal, which pays Chimera $2 million a season in 2014-15 and 2015-16, was announced Friday by the Capitals.
The 34-year-old forward has five goals and six assists in 16 games this season for the Capitals, including a career-best four-game goal streak.
He joined Washington in a trade with the Columbus Blue Jackets in December 2009.
The Capitals are 9-7 this season and have won four consecutive games after a 3-2 shootout victory against the Minnesota Wild on Thursday night.
Washington plays at Phoenix on Saturday.