Farentino appeared three times on Broadway: in the original production of Tennessee Williams' The Night of the Iguana, as Stanley in the 1973 revival of Williams' A Streetcar Named Desire, for which he won a Theatre World Award, and as Biff in the 1975 revival of Arthur Miller's Death of a Salesman opposite George C. Scott. He also received the Joseph Jefferson Award for One Flew Over the Cuckoo's Nest the Arlington Park Theatre in Chicago, Illinois.

He received a Golden Globe Award for The Pad and How to Use It and an Emmy Award nomination for the miniseries Jesus of Nazareth. Farentino also appeared in dozens of films and television series including Me Natalie, Dynasty, Melrose Place, The Bold Ones: The Lawyers, and ER.

Farentino was married four times, including unions with actresses Michele Lee and Elizabeth Ashley. He is survived by two sons, David and Saverio.