Lithgow is known for his roles as Dr. Dick Solomon on the NBC sitcom 3rd Rock from the Sun, Arthur Mitchell on Showtime's Dexter and Reverend Shaw Moore in Footloose. He appeared in the films The World According to Garp (1982) and Terms of Endearment (1983), receiving the Academy Award nomination, Best Actor in a Supporting Role for each.

On the stage, he appeared in the musical adaptation of Sweet Smell of Success, winning the Tony Award for Best Leading Actor in a Musical. He again appeared in a musical, Dirty Rotten Scoundrels, receiving the Tony nomination for Best Leading Actor in a Musical.

He has also recorded music, such as the 1999 album of children's music, Singin' in the Bathtub, and has written poetry and short stories for children, such as Marsupial Sue.

Lithgow was born in Rochester, New York, USA. His mother, Sarah Jane (née Price), was a retired actress, and his father, Arthur Lithgow, was a theatrical producer and director who ran the McCarter Theatre in Princeton, New Jersey. Because of his father's job, the family moved frequently during Lithgow's childhood, including teenage years in Akron and Lakewood, Ohio.

Lithgow attended Harvard University, where he graduated magna cum laude in 1967. He lived in Dunster House as an undergraduate, across the hall from roommates former Vice President Al Gore and actor Tommy Lee Jones. Lithgow later served on its Board of Overseers. Lithgow credits a performance at Harvard of Gilbert and Sullivan's Utopia Limited with helping him decide to become an actor. After graduation, Lithgow won a Fulbright Scholarship to study at the London Academy of Music and Dramatic Art.

In 1973, Lithgow debuted on Broadway in David Storey's The Changing Room, for which he received both the Tony and Drama Desk Award as Best Featured Actor in a Play. The following year he starred opposite Lynn Redgrave in My Fat Friend and in 1976 played opposite Meryl Streep in Arthur Miller's A Memory of Two Mondays. He was nominated for two Best Actor Tonys for Requiem for a Heavyweight (1985) and M. Butterfly (directed by John Dexter, 1988).

In 2002, Lithgow won a Tony Award for Best Leading Actor in a Musical for his portrayal of J.J. Hunsecker in the Broadway adaptation of the 1957 film Sweet Smell of Success. In 2005, Lithgow was elected into the American Theatre Hall of Fame for his work on Broadway. He was also nominated for a Best Leading Actor in a Musical Tony for Dirty Rotten Scoundrels.

In 2008 through 2009, Lithgow played Joe Keller in a Broadway revival of Arthur Miller's All My Sons.

Lithgow stars alongside Jennifer Ehle in the production of Douglas Carter Beane's comedy Mr & Mrs Fitch presented Off-Broadway by Second Stage Theatre from February 22, 2010, closing April 4, 2010.

In 1979, Lithgow portrayed the role of Lucas Sergeant in Bob Fosse's semi-autobiographical movie All That Jazz. The character was loosely based on the real-life director/choreographer Michael Bennett, best known for his work on Dreamgirls and A Chorus Line.