Born in Milan, Milli formed under Giorgio Strehler at the Piccolo Teatro di Milano, where he debuted in 1951 and where he was active until 1953.

[1][2] In the 1960s and in the 1970s he worked intensively with director Luigi Squarzina and at the Teatro Stabile in Genoa, specializing in the Carlo Goldoni repertoire.

[1][2] Milli was also active as a character actor in films, mainly cast in humorous roles, often as a sidekick of Paolo Villaggio.

[1][2] On television, he is best known for the role of Ugo Monti in the Canale 5 TV series CentoVetrine.

[1][2] Milli died from COVID-19 complications on 20 January 2022, at the age of 92.