Early life and career
Andersson was born in Kungsholmen, Stockholm, the daughter of Karin (née Mansion), a social worker, and Josef Andersson, a businessman.
Her first collaboration with Ingmar Bergman came in 1951, when she participated in his production of an advertisement for the detergent Bris. She also worked as an extra on film sets as a teenager, and studied acting at the Terserus Drama School and at the Royal Dramatic Theatre School (1954–1956). She then joined the Royal Dramatic Theatre in Stockholm.
In the 1950s, 1960s, and 1970s, Andersson starred in ten motion pictures and three television films directed by Bergman. With Ingrid Thulin and Eva Dahlbeck, she shared the Best Actress Prize at the 1958 Cannes Film Festival for the director's Brink of Life, a film set in a maternity ward. The others included The Seventh Seal, Wild Strawberries, The Magician, The Passion of Anna, The Touch, and Persona.
In 1963, Andersson won the Silver Bear for Best Actress at the 13th Berlin International Film Festival for her performance in Vilgot Sjöman's The Mistress.