Deitch was born in Chicago on August 8, 1924 to Joseph Deitch and Ruth Delson Deitch. In 1929, the family moved to Los Angeles where he attended school.
After graduating from Los Angeles High School, Deitch began working for North American Aviation, drawing aircraft blueprints. In 1943, he was drafted and underwent pilot training before catching pneumonia,leading to his honorary discharge in May of the following year.
Deitch worked a variety of jobs before taking up an apprenticeship at the animation studio, United Productions of America (UPA) in 1955, later becoming the creative director of Terrytoons. There he created such characters as Sidney the Elephant, Gaston Le Crayon,Tom Terrific, and Clint Clobber.
While still working at UPA, Deitch wrote and drew the United Feature Syndicate comic strip The Real-Great Adventures of Terr’ble Thompson!, Hero of History, starring a courageous child in fantastical adventures.
In early 1958, his theatrical cartoon Sidney’s Family Tree was nominated for an Academy Award and later that year in August Terrytoons laid him off. Deitch set own studio in New York called Gene Deitch Associates, Inc, which primarily produced television commercials.
In October 1959,after an offer from client Rembrant Films to fund Munro,an animated theatrical short Deitch wanted to create,he relocated to the company’s base in Prague, Czechoslovakia,where he met his second wife,Zdenka.
Munro premiered in Czechoslovakia in September 1960 and in the U.S. on October 5, 1961, as a short preceding Breakfast at Tiffany’s. It won an Academy Award for Best Animated Short Film in 1961, making it the first short outside of the United States to receive such an honor.
From 1960 to 1963, Deitch collaborated with Rembrandt to direct Popeye cartoons for television with King Features, and from 1961 to 1962 he directed 13 new Tom and Jerry shorts for MGM.
With producer William L. Snyder, Deitch co-produced and directed a series of TV shorts of Krazy Kat for King Features from 1962 to 1964. He also co-producedThe Bluffers, which was based on one of Deitch’s ideas and directed the 1966 film Alice of Wonderland in Paris.
In 1966, he worked with Czech animator Jiří Trnka on a feature-length animated film adaptation of The Hobbit. However, producer William L. Snyder couldn’t secure the funds, and in order to not let the rights for the novel expire, he asked Deitch to produce a short film adaptation in 30 days. Deitch and illustrator Adolf Born made a 13-minute animated film never intended for distribution; the film was long considered lost until it was rediscovered by Snyder’s son and released on YouTube in 2012.
From 1969 until his retirement in 2008, Deitch was the leading animation director for the Connecticut organization Weston Woods Studios, adapting children’s picture books. Deitch adapted 37 films for Weston Woods, from Drummer Hoff in 1969 to Voyage to the Bunny Planet in 2008.
In 2003, Deitch was awarded the Annie Awards’ Winsor McCay Award by ASIFA-Hollywood for a lifetime contribution to the art of animation.
Deitch met his first wife, Marie, when they both worked at North American Aviation, and they got married in 1943.Together they had three sons; Kim, Simon, and Seth Deitch.
He got married to his seconds wife Zdenka Najmanová , the production manager at the studio Bratři v triku where he worked in 1964.
Deitch died in Prague on April 16, 2020, at the age of 95. Shortly before his death, Deitch had noted intestinal problems.