Malleson was born in Croydon, Surrey, England and educated at Brighton College. Despite his unassuming appearance, he was married three times, and had many relationships. In 1915, he married the aspiring actress Lady Constance Annesley. Like her, he was interested in social reform, one of his plays being on the subject of the Tolpuddle Martyrs. They were divorced in 1923 and Malleson later married Joan Billson, who died in 1956. His third wife was Tatiana Lieven.
His best-known films include...
- Tudor Rose (1936) as the Duke of Suffolk
- Major Barbara (1941) as Morrison the butler
- Dead of Night (1945) as the undertaker
- Kind Hearts and Coronets (1949) as Mr Elliott the hangman
- The Man in the White Suit (1951) as the Tailor
- The Importance of Being Earnest (1952) (as Canon Chasuble)
- Private's Progress (1956) as Windrush Snr
- Brothers in Law (1957) as Kendall Grimes
- I'm All Right Jack (1959) as Windrush Snr
Malleson was also a writer on many films, including some of those in which he had small parts, such as Nell Gwyn (1934) and The Thief of Bagdad (1940).