Kamdjo, 25, played in only five games for Forest Green last season, but made 33 appearances on loan at Boreham Wood.
He started his career with Reading, and had spells at Barnet and Salisbury before joining Rovers in 2014.
York were relegated from League Two last season after winning only seven league games.
York City have signed midfielder Clovis Kamdjo on a two-year contract following his release by National League rivals Forest Green Rovers in May.