The Nationals said Wednesday that they gave the Marlins international slot value in the deal.
The hard-throwing Barraclough went 1-6 with 4.20 ERA and 10 saves in 17 chances, with 61 appearances this year. He allowed one hit in 36 at-bats in June, when he was chosen NL reliever of the month, but struggled with his command the rest of the season.
Barraclough's ERA ballooned to 10.24 over his final 24 games and he lost the Marlins closer's job.
He has a career ERA of 3.21 with 279 strikeouts and 134 walks in 218 2/3 innings over four seasons, all with Miami.
Washington general manager Mike Rizzo is in need of relievers after jettisoning Shawn Kelley and Brandon Kintzler late this season.
The deal helps the Marlins in their pursuit of top international free-agent Victor Victor Mesa, a Cuban outfielder who tried out for major league scouts at Marlins Park last week.
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