His parents, Mariantonia Angello and Filippo Castellano, were Italian immigrants from Castrofilippo, Sicily.

[3] After his death, Castellano's widow Ardell Sheridan, who had played his character Peter Clemenza's wife in The Godfather,[4][5] claimed that he was the nephew of Gambino crime family boss Paul Castellano;[6] however Richard's own sister dismissed this claim as false: "we're not related to Paul".

[7] Castellano gained worldwide fame for his role in Lovers and Other Strangers (1970), for which he was nominated for an Academy Award.

[citation needed] Castellano did not reprise his role as Clemenza in The Godfather Part II (1974).

Bruno Kirby portrayed Clemenza as a young man in The Godfather Part II.