Hughes, a cornerback from Oregon State, is the first member of the 2009 draft class to sign.
He played for former Chargers coach Mike Riley and finished his college career with 178 tackles and three interceptions.
Also Friday, the Chargers releases guard Sam Allen, cornerback Ramarcus Brown, wide receiver Jeremy Childs and linebacker Anthony Felder. All were rookie free agents.
Copyright 2009 by The Associated Press