The Seahawks signed the linebacker Wednesday, Ian Rapoport of NFL Media reports.
Nicolas appeared headed to Cleveland two weeks ago when the Browns and Chiefs agreed to a player-for-player deal with tight end Randall Telfer headed to Kansas City. But the teams called off the trade and released the players.
The Chiefs made Nicolas a sixth-round pick out of Virginia Tech in 2016. He played 11 games as a rookie, though seeing only 28 snaps on defense and 45 on special teams.
Nicolas, 25, missed last season with a knee injury.