Trained in New York's Works Progress Administration Dramatic Workshop, he spent the war years touring with Maurice Evans' G.I. Hamlet, appearing with another young hopeful, Howard Morris. After the war he accumulated scores of stock company and Broadway credits, then in 1948 made his television debut in the short-lived series Fashion Story. While starring in NBC's 54th Street Revue, he was hired as one of the regulars on Your Show of Shows, appearing on a weekly basis with Sid Caesar, Imogene Coca, and old pal Howie Morris. During the scripting sessions for Show of Shows, Reiner became friends with a bombastic staff writer named Mel Brooks, with whom he improvised a number of wild stream-of-consciousness comedy bits that would eventually crystallize as the classic "2000 Year Old Man" routines.

An Emmy winner for his work on the various Sid Caesar programs, he entered films as a character actor in 1959. That same year, he wrote, produced, and starred in the pilot episode for a proposed series about a comedy writer named Rob Petrie, titled Head of the Family. The network executives liked the concept, but vetoed Reiner as the star; swallowing his pride, he retooled the property with another leading man, and that's how the Emmy-winning Dick Van Dyke Show was born. During the series' five-year run, Reiner made innumerable cameo appearances on the program, most memorably as Rob Petrie's mercurial TV-comedian boss Alan Brady. In 1967 he made his film directorial debut with Enter Laughing, an adaptation of his own semi-autobiographical 1958 novel (the book had already been transformed into a Broadway play with Alan Arkin as star). Reiner's later directing assignments included The Comic (1967), a bittersweet farce based on the lives of Stan Laurel, Harry Langdon, and Buster Keaton; the black comedy cult favorite Where's Poppa? (1970); the whimsical fantasy Oh, God (1977); and a popular series of Steve Martin vehicles, among them The Jerk (1978) and Dead Men Don't Wear Plaid (1982).

His film output decreased in number and quality in the l980s and 1990s, though critics enjoyed his offbeat 1989 working-class comedy Bert Rigby, You're a Fool and his 1997 Bette Midler starrer That Old Feeling. In 1995, he earned yet another Emmy Award for his revival of the Alan Brady character on a memorable episode of TV's Mad About You. In 2001 he began appearing in Steven Soderbergh’s Ocean’s series of films with a role in Ocean’s Eleven, then two years later he released his memoir, My Anecdotal Life. To celebrate the 50th anniversary of Reiner’s character the 2000 Year Old Man, the Shout Factory label released the three-CD/one-DVD box set The 2000 Year Old Man: The Complete History in 2009. Carl Reiner is the father of directors Rob Reiner and Lucas Reiner; his wife Estelle has enjoyed a latter-day career as a nightclub singer and as a cameo performer in her son Rob's films (she's the lady who says, "I'll have what she's having!" in When Harry Met Sally). ~ Hal Erickson