Born in Paris, Jean Cussac studied lyrical singing at the Conservatoire de Paris, and subsequently turned to jazz and joined The Swingle Singers at their creation in 1962, alongside Anne Germain [fr], Jeanette Beaucomont, Christiane Legrand, Jean-Claude Briodin [fr], Claude and José Germain.
Also in 1964, he was chosen to be the singing voice of the prince during the redubbing of Snow White and the Seven Dwarfs.
His contributions included One Hundred and One Dalmatians, The Sword in the Stone, Mary Poppins, The Jungle Book and Pinocchio.
He also took part in the recording of songs from French films such as The Umbrellas of Cherbourg (1964) and Moi y'en a vouloir des sous [fr] (1973) and to albums such as L'Aigle noir by Barbara (1970) and Les Chansons de Sylvain et Sylvette.
He also continued his recording career, including the Coronation Mass by Mozart, Les Malheurs d'Orphée by Darius Milhaud alongside Claudine Collart [fr], Janine Collard [fr], Jacqueline Brumaire, Bernard Demigny and André Vessières.