Blackmon's agent, Peter J. Schaffer, confirmed the agreement in an email to The Associated Press on Tuesday.
The Redskins signed Blackmon, 31, after the first week of the 2015 season and he ended up starting 10 games. He played in 15 games, intercepted two passes and forced three fumbles.
He played in the slot as well as on the outside for Washington.
Blackmon has played with three other teams -- four years with Green Bay and two each with the New York Giants and Jacksonville. He was released by Seattle last summer.
Blackmon has played more than nine games only three times in his career.