Born James William Ercolani in Philadelphia, Pennsylvania in 1936, Darren began his career as a teen idol, having been discovered by talent agent and casting director Joyce Selznick. This encompassed roles in films, most notably his role as Moondoggie in Gidget in 1959, as well as a string of pop hits for Colpix Records.
His biggest hit was "Goodbye Cruel World" (#3 on the Billboard Hot 100 in 1961). It sold over one million copies, and was awarded a gold disc. Another hit was "Her Royal Majesty" (#6 on the Billboard Hot 100 in 1962). He is also featured in one of the Scopitone series of pop music video jukebox films ("Because You're Mine.")
Darren had a regular role as Officer James Corrigan on the television police drama T.J. Hooker from 1983–1986. Subsequently he worked as a director on many action-based television series, including Hunter, The A-Team, and Nowhere Man, as well as dramas such as Beverly Hills, 90210 and Melrose Place.
In 1998, he achieved renewed popularity as a singer through his appearances on Star Trek: Deep Space Nine in the role of holographic crooner and advice-giver Vic Fontaine. Many of his performances on the show were re-recorded for the album This One's From the Heart released in 1999. The album featured Darren, a close friend of Frank Sinatra, comfortably singing in the Sinatra style; the 2001 follow-up Because of You showed similar inspiration from Tony Bennett.
He was the singing voice of Yogi Bear in the 1964 animated film, Hey There, It's Yogi Bear!, on the song "Ven-e, Ven-o, Ven-a". Prior to that, he was the singing and speaking voice of "Jimmy Darrock" on an episode of The Flintstones.
In addition to sharing a birthday with Nancy Sinatra, he and his wife are godparents to her daughter Angela Jennifer Lambert; Frank Sinatra's first grandchild.