San Francisco also announced that safety Antone Exum signed his one-year contract Friday that had been agreed to earlier in the week.
Marsh was one of the team’s top edge rushers last year with 5½ sacks but became expendable after the team traded for Dee Ford this week and gave him a new five-year contract.
Nzeocha has played in 26 games the past two seasons and has been a standout on special teams. He started three games last year at linebacker and provides depth at the position.
Exum spent the past two seasons with the 49ers and started seven games at safety in 2018.