He was born Franco Spartanero in San Prospero and grew up in Bedonia and Milan. He studied briefly at the FacoltÓ di Economia e Commercio before leaving to study at the Piccolo Teatro di Milano.
His first film role was a small part in La Ragazza in Prestito (1964), he had his first lead role in Sergio Corbucci's Django (1966) a Spaghetti Western and one of his most well-known films. In 1966 from Django he went on to appear in eight more films including Texas, Addio and Tempo di Massacro. In 1967 he appeared in his first English language film, Camelot as Lancelot. A certain lack of facility with English tended to limit these roles, although he also appeared in other English language films including The Virgin and the Gypsy (1970), Force 10 From Navarone (1978) and Die Hard 2 (1990). Although often typecast in films like Los amigos (1972) or Keoma (1976) he has attempted an impressive range of characters, like Abel in Huston's epic The Bible (1966) and the gay lieutenant in Querelle (1982). He has appeared in almost 150 films and has written, produced and starred in one - Jonathan degli orsi (1993)
While working on Camelot he became close to Vanessa Redgrave, and in 1969 they had a son, Carlo Gabriel Nero, a screen-writer and director.