Serving in the 104th Infantry Division in the European Theatre, he was near Aachen, Germany when he was wounded, reportedly by a land mine. Recovering from his injuries in the Army Hospital near Cirencester, England, he wrote the book and lyrics to a musical comedy, No T.O. for Love. First produced in 1945 by the Special Services Unit, the show toured European Army bases for two years. The London opening of No T.O. for Love at the Scala Theatre in the West End marked the beginning of Chayefsky's theatrical career. During the London production of this musical, Chayefsky encountered Joshua Logan, a future collaborator, and Garson Kanin, who invited Chayefsky to join him in working on a documentary of the Allied invasion, The True Glory.
Returning to the United States, Chayefsky worked in his uncle's print shop, Regal Press, an experience which provided a background for his later teleplay, A Printer's Measure. Kanin enabled Chayefsky to spend time working on his second play, Put Them All Together (later known as M is for Mother), but it was never produced. Chayefsky was married to Susan Sackler in February 1949, and their son Dan was born six years later. Despite an alleged affair with Kim Novak, Paddy and Susan Chayefsky remained together until his death.
Chayefsky died in New York City of cancer in August 1981 at the age of 58, and was interred in Kensico Cemetery in Valhalla, Westchester County, New York.
Chayefsky gained the reputation as the pack leader of kitchen sink realism on television. Between 1949 and 1955, he delivered a dozen teleplays to Coe, including The Bachelor Party and The Catered Affair. One of these teleplays, Mother (April 4, 1954), received a new production October 24, 1994 on Great Performances with Anne Bancroft in the title role. Curiously, original teleplays from the 1950s Golden Age are almost never revived for new TV productions, so the 1994 production of Mother was a conspicuous rarity.
Following the Philco years, Chayefsky's The Great American Hoax was seen May 15, 1957 during the second season of The 20th Century Fox Hour. This was actually a rewrite of his earlier Fox film, As Young as You Feel (1951) with Monty Woolley and Marilyn Monroe. In recent years, The Great American Hoax received showings on the FX channel when Fox did restorations of The 20th Century Fox Hour episodes and brought them back to TV under the title Fox Hour of Stars.
Chayefsky had a unique clause in his Marty contract that stated only he could write the screenplay, and the success of the live TV drama led to a film two years later, starring Ernest Borgnine in the lead role. The movie won the Academy Award for Best Picture. Chayefsky's work on that and other teleplays inspired comparisons with Arthur Miller, and he received an Academy Award for his work on the screenplay.
He focused on screenplays after the success with Marty, with films such as The Goddess, which starred Kim Stanley (for which he received an Oscar nomination) and The Bachelor Party. In the 1960s his writing credits included The Americanization of Emily, which featured James Garner, Julie Andrews, Melvyn Douglas and James Coburn; and Paint Your Wagon, a screen vehicle for Lee Marvin. He went on to win two more Oscars for his work on The Hospital (1971) which starred George C. Scott and Diana Rigg, and Network (1976), which featured Faye Dunaway, William Holden, Peter Finch (who won the Oscar for "Best Actor in a Leading Role") and Robert Duvall among other cast members. For both of these films Chayefsky also received Golden Globe awards. Chayefsky also received an Academy Award for Network in the "Best Original Screenplay" category.
He is known for his comments during the 1978 Oscar telecast after Vanessa Redgrave made a controversial speech denouncing the "Zionist hoodlums" who had threatened her (in reference to threats from the Jewish Defense League, identified by the FBI as a right-wing terrorist group), while accepting her award for Best Supporting Actress in Julia. Two hours later, after no one had commented on her speech, while presenting an award Chayefsky stated his distaste for Redgrave's using the award event to make a political point. He said, "I would like to suggest to Miss Redgrave that her winning an Academy Award is not a pivotal moment in history, does not require a proclamation and a simple 'Thank you' would have sufficed." He received loud applause for his riposte to Redgrave. Later, in an interview, he stated that he was offended by her "cracks about Jews" and about having sat and "praying somebody would say something" and commented only because no one did.