Hird married musician James Scott in 1937. They had a daughter, Actress Janette Scott, in 1938. Hird was widowed in 1994, having been married for 57 years.
Although Hird left Morecambe in the late 1940s, she retained her affection for the town, referring to herself as a "sand grown 'un", the colloquial term for anyone born in Morecambe.
Initially, she made regular appearances in films, including the wartime propaganda film Went the Day Well? (1942, known as 48 Hours in the USA), in which she is shown wielding a rifle to defend a house from German paratroopers. She worked with the British film Comedian Will Hay and featured in The Entertainer (1960), which starred Laurence Olivier, as well as A Kind of Loving (1962) with Alan Bates.
Thora Hird gained her highest profile in television comedy, notably the sitcoms Meet the Wife (1963–66), In Loving Memory (1979–86), Hallelujah! (1983–84), and for nearly two decades as Edie Pegden in Last of the Summer Wine (1986–2003). However, she played a variety of roles, including the nurse in Romeo and Juliet, and won BAFTA Best Actress awards for her roles in two of Alan Bennett's Talking Heads monologues.
She was the subject of This Is Your Life on two occasions: in January 1964 when she was surprised by Eamonn Andrews, and in December 1996, when Michael Aspel surprised her while filming on location for Last of the Summer Wine.
She was created an Officer of the Order of the British Empire (OBE) in the 1983 Birthday Honours and raised to Dame Commander (DBE) in the 1993 Birthday Honours. She received an honorary D.Litt. from Lancaster University in 1989.
In December 1998, using a wheelchair, Dame Thora played a brief but energetic cameo role as the mother of Dolly on Dinnerladies, a sarcastic character who was particularly bitter towards her daughter.
A memorial Service was held on 15 September 2003 at Westminster Abbey attended by more than 2000 people, including Alan Bennett, Sir David Frost, Melvyn Bragg and Victoria Wood.