The agreement announced Thursday will make the Smithsonian Channel available to Comcast Digital TV customers. The distribution deal in the Smithsonian's hometown comes three years after the channel's debut.
The Smithsonian Channel said it plans to continue its expansion to the Washington suburbs throughout this year.
The TV unit was launched in 2007, initially as a high-definition channel on DirecTV. It has since expanded to include distribution deals with Time Warner Cable, Cablevision, Verizon and others.
The channel draws stories and programs largely from the world's largest museum complex.