Born in Blackburn, Lancashire, Harrison was one of the first 84 pupils of St Saviour's and St Olave's Church of England School in 1903. She studied at RADA in 1914–15, and then spent some years living in Argentina and Madeira before making her professional acting debut in the UK in the 1920s.
Harrison made her stage debut as Mrs. Judd in The Constant Flirt at the Pier Theatre, Eastbourne in 1926. The following year she appeared in London's West End for the first time as Winnie in The Cage at the Savoy Theatre. Her subsequent West End plays included A Damsel in Distress, Happy Families, The Merchant and Venus, Lovers' Meeting, Line Engaged, Night Must Fall—also acting in the 1937 film version—Flare Path, The Winslow Boy and Watch It Sailor!.
She had already made her film debut with a minor role in Our Boys (1915), when she appeared in the film Hobson's Choice (1931). Another 50 films followed, including Gaslight (1940), In Which We Serve (1942) and Caesar and Cleopatra (1945), before making her name in later films.
Before and during World War II, she played small parts in numerous British films, including The Ghost Train (1941), 'Temptation Harbour (1947), Oliver Twist (1948) and a small but scene-stealing role as Mrs. Dilber in Scrooge (US: A Christmas Carol, 1951).
Harrison also played Kaney in The Ghoul (1933) and the matriarch in Mrs. Gibbons' Boys (1962), as well as two BBC productions of Charles Dickens's novels, Martin Chuzzlewit (1964) and Our Mutual Friend (1976). She later commented that Dickens was her favourite author. As her cinema appearances became more infrequent, Harrison turned to television. She starred on television as Mrs Thursday (1966–67), a charwoman who inherits £10 million and the controlling interest in a major company.
The Huggett family made their first appearance in Holiday Camp (1947). Harrison played the London East End charwoman Mrs Huggett. The actress continued with the role, alongside Jack Warner as her screen husband, in Here Come the Huggetts (1948), Vote for Huggett and The Huggetts Abroad (both 1949), as well as a radio series, Meet the Huggetts, which ran from 1953 to 1961. Although disliked by critics, almost immediately it became one of the most popular programmes of its day. Harrison turned down the title role in writer Jeremy Sandford's Play for Today Edna, the Inebriate Woman (1971).
Harrison also starred with Warner in the film Home and Away (1956), about a working-class family that wins the football pools.
Harrison married John Henry Beck in 1916; the couple had three children, two sons and a daughter. She always pretended to be six years younger than her age, but in 1992 she owned up to reaching 100 and received her telegram from the Queen. Harrison died in 1995 at the age of 103. She was predeceased by her husband John and a son.