Born to an American father of English descent and a Canadian mother of Irish and Scottish ancestry, MacLaine graduated from high school and moved to New York City to live out her dream of being a Broadway actress. She achieved her goal when she became understudy to actress Carol Haney in The Pajama Game; Haney broke her ankle and MacLaine replaced her. A few months thereafter, with Haney still out of commission, director/producer Hal B. Wallis was in the audience, took note of MacLaine, and signed her to go to Hollywood to work for Paramount Pictures.

Her first film was the Alfred Hitchcock film The Trouble with Harry in 1955. Her film career is now in its fifth decade. MacLaine was nominated for the Academy Award for Best Actress in a Leading Role five times: in 1958 for Some Came Running, in 1960 for The Apartment, in 1963 for Irma La Douce, in 1977 for The Turning Point and in 1983 for Terms of Endearment (which she finally won). In 1975, she also received a nomination for Best Documentary Feature for her documentary The Other Half of the Sky: A China Memoir. She recently appeared as the maternal grandmother to Cameron Diaz and Toni Collette in In Her Shoes. MacLaine was also the only female member of the infamous Rat Pack, alongside Frank Sinatra, Dean Martin and Sammy Davis, Jr..