DuVall was born in Los Angeles, California, the only child of Rosemary (née Hatch) and Stephen DuVall. Her parents divorced when she was 12. After her mother remarried, DuVall dropped out of high school and moved into her own apartment. She sought entertainment in movies and television programs, memorizing entire scenes. DuVall decided she wanted to be an actress, and returned to high school, this time the Los Angeles County High School of the Arts, while working to support herself. She is not related to actors Robert Duvall or Shelley Duvall, who share their surnames with her.