The Redskins signed rookie Graham Gano after kicking tryouts at Redskins Park, the team said in a release.
Washington, languishing in last place in the NFC East at 3-9, also announced that top running back Clinton Portis would miss the rest of the season by placing him on injured reserve because of a concussion.
Portis, who rushed for 494 yards on 124 carries this season, suffered the injury against the Atlanta Falcons on November 8 and has missed the last four games.
Gano, 22, played this season with the United Football League's Las Vegas Locomotives, where he converted 13-of-16 field goal attempts and all 20 extra points.
Suisham hit 18 of 21 field goals this season but missed two key field goals in a 7-6 loss to Dallas on November 22 and a 23-yarder against the Saints that would have given Washington a 10-point lead with less than two minutes to play.
New Orleans (12-0) tied the score on their ensuing possession and won the game 33-30 in overtime.
Suisham joined the Redskins during the 2006 season and converted 81 of 101 field goal attempts in 49 games.
(Writing by Steve Ginsburg; Editing by Justin Palmer and Sonia Oxley)