Maschwitz started his stage acting career in the early 1920s and joined the BBC in 1926. His first radio show was In Town Tonight and his first television show was The Black and White Minstrels. In 1939, he went to Hollywood under contract to MGM, where he worked on Goodbye Mr Chips and Queen of Song, among other successful films.
During the Second World War, he served with the Intelligence Corps and became Chief Broadcasting Officer with the 21st Army Group. He left the army as a Lieutenant Colonel.
In 1958, at the start of the BBC/ITV ratings wars, he rejoined the BBC as Head of TV Light Entertainment. About the job he said, "I don't think the BBC is a cultural organisation. We've got to please the people. The job of a man putting on a show is to get an audience." Maschwitz left to join the rival ITV in 1963.
During the course of his varied entertainment career, Maschwitz adapted French comedies like Thirteen For Dinner; wrote the book and lyrics for numerous musicals, amongst them Balalaika, Summer Song and Zip Goes a Million; and created Café Collette. He also edited the Radio Times, turned The Ghost Train into a musical and wrote the words for A Nightingale Sang In Berkeley Square and These Foolish Things.
Eric Maschwitz was first married to Hermione Gingold, who was granted a divorce in 1945. He married Phyllis Gordon the same year.