He has starred in a number of well-known films, including Goodbye, Columbus (1969), Catch-22 (1970), Portnoy's Complaint (1972), Westworld, The Last of Sheila (both 1973) and Saturday the 14th (1981).

In 1968, Benjamin was nominated for an Emmy Award for Best Actor in a Comedy Series for his performance on the CBS sitcom He & She (starring opposite his wife Paula Prentiss), which aired from 1967-1968.

In 1976, Benjamin received a Golden Globe Award for Best Actor in a Supporting Role - Motion Picture for his performance as aged vaudevillian Willy Clark's (Walter Matthau) comedically long-suffering nephew, confidant and talent agent, Ben Clark, in Herbert Ross' The Sunshine Boys (1975), based on Neil Simon's 1972 hit stage play of the same name.

After directing for television, his first film as a director was the 1982 comedy My Favorite Year, starring Peter O'Toole, who was nominated for an Oscar for Best Actor.

[3] Benjamin's first lead role in a film came with an adaptation of the Philip Roth novella, Goodbye, Columbus (1969) with Ali MacGraw.

He then acted in two more successful films, as part of an all-star cast in The Last of Sheila (1973), from a script by Anthony Perkins and Stephen Sondheim, and in Westworld (1973), directed by Michael Crichton and co-starring Yul Brynner.

The Los Angeles Times stated that by this stage, his image was of "a whining, petulant bore by doing too good a job of acting in a series of sleazy roles."

Benjamin played a frustrated fiancé of a woman who falls for the vampire Count Dracula in the surprise box-office smash Love at First Bite (1979) starring George Hamilton and Susan Saint James.

Benjamin had supporting roles in The Last Married Couple in America (1980), How to Beat the High Co$t of Living (1980), Witches' Brew (1980), and First Family (1980).

Benjamin's second feature as director was Racing with the Moon (1984) from a script by Steve Kloves starring Sean Penn and Nicolas Cage.

He was then called in at short notice to replace Blake Edwards on City Heat (1984) with Clint Eastwood and Burt Reynolds, which was a critical and commercial disappointment.

[13] Benjamin directed a comedy for Steven Spielberg's company, The Money Pit (1986) with Tom Hanks and Shelley Long.

In the 1990s, Benjamin returned to acting with appearances on shows including The Ray Bradbury Theater, Love & War, Ink, Mad About You, and Titus, as well as the films Deconstructing Harry (1997),[14] Keeping Up with the Steins (2006), and Henry Poole Is Here (2008).

[15] Benjamin did some directing for TV – The Pentagon Wars (1998), Tourist Trap (1999), The Sports Pages (2001), and Laughter on the 23rd Floor (2001) from the play by Neil Simon.

In 2006, Benjamin directed the award-winning cable television drama A Little Thing Called Murder, starring Australian Judy Davis.

He most recently played Dr. Green in the Netflix comedy film You People (2023) opposite Jonah Hill and Julia Louis-Dreyfus.