He was born in London's East End, the son of Jewish immigrants from Kiev, Ukraine. Leaving school at 15, Feldman started his show-business career as a trumpet player (like Spike Milligan) but soon turned to comedy. He formed a flourishing writing partnership with Barry Took in 1954. For British television they wrote situation comedies such as The Army Game, Bootsie and Snudge, and most notably the ground-breaking BBC radio show Round the Horne, which starred Kenneth Horne and Kenneth Williams. Feldman was also a writer on The Frost Report with several future members of Monty Python.

The television sketch comedy series At Last the 1948 Show featured Feldman's first on-screen performances. In one memorable sketch, first broadcast on March 1, 1967, Feldman harassed a patient shop assistant (John Cleese) for a series of fictitious books, finally achieving success with Ethel the Aardvark goes Quantity Surveying. The sketch was revived as part of the Monty Python stage show repertoire, and on Monty Python's Contractual Obligation Album (both without Feldman).

Marty Feldman was co-author, with John Cleese, Graham Chapman and Tim Brooke-Taylor, of the "Four Yorkshiremen" sketch, which was written for their television comedy series At Last the 1948 Show. The "Four Yorkshiremen" sketch was performed during Amnesty International concert performances (by members of Monty Python - one time including Rowan Atkinson in place of Monty Python member Eric Idle), as well as being performed during Monty Python Live at the Hollywood Bowl and other Monty Python shows and record albums (and now on CDs). This has led to the inevitable result of the "Four Yorkshiremen" sketch now being considered a Monty Python sketch, with the origin of the sketch, and the co-authorship of the sketch by non-Monty Python writers Marty Feldman and Tim Brooke-Taylor, being unfortunately overlooked, or forgotten, by many people.

Following his success on At Last the 1948 Show, Feldman had a memorable series of his own shows on the BBC called Marty (1968), which also featured Tim Brooke-Taylor, John Junkin and Roland MacLeod. The second series (made in 1969) was renamed It's Marty (with the second title being retained for the DVD release of the show). In 1974, Denis Main Wilson (producer for the UK television show Till Death Us Do Part) produced a short sketch series for Feldman entitled Marty Back Together Again - a reference to reports about the star's health. But this series never recaptured the impact of the earlier series.

Marty Feldman's performances on American television included The Dean Martin Show and Marty Feldman's Comedy Machine. He is best remembered for his role as the hunchback Igor (pronounced as eye-gor) in Young Frankenstein - in which, as usual, many of his lines were improvised.

He also released one long playing record called I Feel A Song Going Off (1969), re-released as The Crazy World of Marty Feldman. The songs were written, not by him, but by Dennis King, John Junkin and Bill Solly (a writer for Max Bygraves and The Two Ronnies).1

Feldman appeared in The Adventure of Sherlock Holmes' Smarter Brother and several Mel Brooks films, including Silent Movie and Young Frankenstein. He directed and starred in The Last Remake of Beau Geste and died from a heart attack (as a result of shellfish food poisoning) in a hotel room in Mexico City, Mexico during the making of the film Yellowbeard.

Mel Brooks on the DVD commentary of Young Frankenstein, cites a number of factors that may have contributed to Feldman's early death from a heart attack. He was a very heavy smoker (smoking half a carton of cigarettes a day), drank copious amounts of coffee, and, although a vegetarian, ate a diet high in eggs and other dairy products. The increased stress placed upon his body by the high altitude environment of Mexico City (it is located at an altitude of 2,300m where the air contains 30ess oxygen than at sea level) was very probably also a contributory factor in his sudden death.

He is buried in Forest Lawn Memorial Park (Hollywood Hills), Los Angeles, California near his idol, Buster Keaton, in the Garden of Heritage, lot 5420.

It was long thought that he was brother to actress Fenella Fielding, but the actress has debunked this notion.