He began his career appearing in films, radio dramas, television and theatrical productions in the late 1940s.

In 1960, he played the villainous Haman in Esther and the King, starring Joan Collins and Richard Egan in the title roles.

Among his roles in the UK, Fantoni appeared alongside Anglo-Italian actress Cherie Lunghi in the Channel 4 television series The Manageress.

[3] He also provided voice-overs for Henry Fonda, Rock Hudson, Gregory Peck, Ben Kingsley, Max von Sydow and Robert Taylor in at least one or two of their movies.

Fantoni was married to actress Valentina Fortunato (whom he met at the Piccolo Teatro in Milan in 1954) from 1961 until her death in 2019.