Carr was born Charmian Anne Farnon in Chicago, Illinois, the second child of vaudeville actress Rita Oehmen and musician Brian Farnon. The couple divorced in 1957. She had two sisters, both actresses (Shannon Farnon and Darleen Carr). Her family moved to Los Angeles when she was 10. While a student at San Fernando High School, Carr was a cheerleader and played basketball and volleyball. "She had never had a singing lesson and had never tried to act" before she was signed to be in The Sound of Music.