His most notable film roles are Carmine Rosato in The Godfather Part II (1974) and Albert Volpe in The Godfather Part III (1990). He is one of three actors to play two different roles in the Godfather films (the others being Frank Sivero, who played a young Genco Abbandando in Godfather Part II and a bystander to the fight between Sonny Corleone and Carlo Rizzi in The Godfather, and Sofia Coppola, who played Mary Corleone in Godfather Part III and the infant son of Carlo and Connie baptized in the final scenes of The Godfather).
According to studio executive Robert Evans in his 1994 memoir The Kid Stays in the Picture, Caridi was director Francis Ford Coppola's first choice for the role of Sonny Corleone, but Evans insisted on James Caan because Caridi was too tall to play opposite Al Pacino. He appeared in the cult movie classic Kiss Meets the Phantom of the Park (1978), playing amusement park manager Calvin Richards, and appeared as Sam Giancana in the 1992 film Ruby.
On television he portrayed Dan Valenti on Phyllis from 1976-77. In 1978, he appeared as Di Carlo in the episode "The Intimate Friends of Janet Wilde" of the NBC crime drama series The Eddie Capra Mysteries. Between 1982 and 1983, Caridi played Angelo Martelli, Bruno Martelli's father, in the TV series Fame. Caridi went on to play Detective Vince Gotelli in the television series NYPD Blue from 1993-99.
On January 13, 2004, the Academy of Motion Picture Arts and Sciences announced that it had identified a copy of the film Something's Gotta Give, circulated illegally on the Internet, as carrying markings identifying it as coming from a video sent to Caridi in his role as an Oscar voter. Similarly unauthorized copies of The Last Samurai, Mystic River, Big Fish and Master and Commander: The Far Side of the World were also said to have been traced to Caridi. The FBI subsequently began an investigation into the affair.
Later that month, the FBI charged Russell Sprague of Homewood, Illinois with criminal copyright infringement. Federal authorities allege that for at least three years, Caridi had given Sprague his screener copies of approximately 60 movies seeking consideration for the Academy Awards. According to the FBI affidavit, Caridi said that he sent his screeners via Federal Express to Sprague, who gave him FedEx boxes, pre-addressed labels and an account number. Caridi denied receiving money from Sprague, telling the FBI he believed that Sprague was a film buff.
Caridi and Sprague were sued by Sony and Time Warner on civil charges of copyright infringement. The studios are suing in the United States District Court for the Central District of California in Los Angeles, seeking damages of a minimum of $150,000 per movie, with hundreds of individual violations alleged. While awaiting trial on criminal charges, Sprague died of a suspected heart attack.
The Academy of Motion Picture Arts and Sciences announced on February 3, 2004 that it was expelling Caridi for violating his agreement to safeguard their screeners, making him the first Academy member to be expelled under its anti-piracy policy.