He portrayed Johnny Torrio in Boardwalk Empire in every season, from 2010 to 2014,[1] and Phil Leotardo's right-hand man Butch DeConcini in The Sopranos from 2006 to the series finale in 2007.

[3] As an actor, he had roles in The Rockford Files, as Vinnie Morabito on Busting Loose, Tony Manucci on Makin' It, Butch DeConcini on The Sopranos, and Johnny Torrio on Boardwalk Empire.

Antonacci was also a playwright, theatrical actor, and director, participating in multiple productions and roles at the La MaMa Experimental Theater Club in the East Village throughout the early through mid-1970s.

[5] He wrote and performed in the 1971 Off-Off-Broadway musical "Dance Wi' Me (or, The Fatal Twitch)," which was directed by Joel Zwick and produced at La MaMa.

This play was produced again at La MaMa in 1974, and then renamed and re-staged as the Broadway musical "Dance With Me," opening January 23, 1975 at the Mayfair Theatre in New York City.