He was a regular in the films of Miloš Forman including as Fredrickson in One Flew Over the Cuckoo's Nest (1975), Salieri's valet in Amadeus (1984), Jean in Valmont (1989), Chester in The People vs. Larry Flynt (1996), and ABC executive Maynard Smith in Man on the Moon (1999).

Schiavelli is the subject of the biographical film, Tanti Beddi Cosi (English, Many Beautiful Things) about his return to Polizzi Generosa, the historically significant ancestral village of his grandfather.

Schiavelli's first film role occurred in Miloš Forman's 1971 production Taking Off,[1] where he played a counselor who taught parents of runaway teens to smoke marijuana to better understand their children's experiences.

Schiavelli's aptitude and distinctive appearance soon provided him with a steady stream of supporting roles, often in Forman's films, including One Flew Over the Cuckoo's Nest, Amadeus, The People vs. Larry Flynt, Valmont, and the 1999 biopic Man on the Moon.

He appeared as another villain in the James Bond film Tomorrow Never Dies (1997), as a silent monk in The Frisco Kid (1979), and as John O'Connor, one of the evil Red Lectroids in 1984's The Adventures of Buckaroo Banzai Across the 8th Dimension.

In 1994 he appeared in the music video for ZZ Top's "Breakaway", alongside Fairuza Balk and in 1997, was named one of America's best character actors by Vanity Fair magazine.

In Highlander: The Series, he played Leo Atkins, a homeless Vietnam War veteran accused of murder in the Season 1 episode "Innocent Man".