Libertini was born in Cambridge, Massachusetts, and graduated from Emerson College in Boston. During his early years, Libertini worked in New York City and in Chicago. He moved to Los Angeles to pursue his acting career during the 1960s.
Libertini married Actress Melinda Dillon on September 30, 1963, and had one child with her, Richard. They divorced in 1978.
He was an original cast member of The Mad Show, a 1966 Off-Broadway musical-comedy produced by Mad magazine. His first film appearances were in The Night They Raided Minsky's (1968), Don't Drink the Water (1969) and Catch-22 (1970).
He was known for playing character roles and his ability to speak in numerous accents. His films include Catch-22 (1970), The In-Laws (1979), Popeye (1980), All of Me (1984), Fletch (1985), Fletch Lives (1989), Awakenings (1990), Lethal Weapon 4 (1998), and Dolphin Tale (2011).
On television, Libertini was a series regular in the first season of Soap as the Godfather. He appeared in as different characters in two episodes of Barney Miller, "Evaluation" (1978) and "Middle Age" (January 1979). He guest starred in the Star Trek: Deep Space Nine episode "Accession" as a Bajoran named Akorem Laan, and in the Sonny with a Chance episode "Dakota's Revenge" as Izzy, an insane mechanic. He also voiced Wally Llama on Animaniacs, and starred in three short-lived sitcoms: Family Man (1988), in which he played a middle-aged comedy Writer who married a much younger woman and became a father late in life; The Fanelli Boys (1990–1991), in which he played an Italian priest; and Pacific Station (1991–1992), in which he played a police detective.
Two of his more memorable film roles came in the comedies Fletch (1985), in which he played Chevy Chase's character's doubting Editor, a role he repeated in the 1989 sequel Fletch Lives, and The In-Laws (1979), in which he played General Garcia, an insane Latin-American dictator whose closest advisor was a cartoon face drawn on his own hand a la Senor Wences. He portrayed Nosh, an electronics expert who is the childhood best friend of Burt Reynolds's character, in Sharky's Machine (1981).
In September 2008, Libertini appeared on the TV show Supernatural. His final film role was that of a Fisherman in the 2011 film Dolphin Tale. From October 2011 through January 2012, Libertini appeared on Broadway as a rabbi in "Honeymoon Motel," the Woody Allen-penned segment of Relatively Speaking.
Libertini died January 7, 2016, at age 82, in Venice, California, from cancer with which he had been diagnosed two years prior.
