The trade means the Stars have three picks in the second round of this year's draft (Nos. 43, 54 and 61), which began Friday night in Pittsburgh.
Ribeiro, 32, played six seasons for the Stars (461 games) and recorded 123 goals and 284 assists. He had 18 goals and 45 assists in 74 games last season.
"We'd like to thank Mike for his contributions the last six years with the Dallas Stars and wish him well with the Washington Capitals," Stars general manager Joe Nieuwendyk said in a press release.
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