Chagall was born in New York City, to a Jewish family. In 1982, she contracted Guillain–Barré syndrome, recovering sufficiently to be cast in the starring role of Gaby, A True Story.
She is perhaps best known for her role as the dimwitted sidekick, "Val", on the 1990s American television series The Nanny.
She made guest appearances on Just Shoot Me! and Strong Medicine. She also played a mysterious woman in What I Like About You. As Rachel Levin, Chagall appeared in Gaby: A True Story (1987) in the title role as Gabriela Brimmer (for which she was nominated for a Golden Globe - Best Actress in a Motion Picture - Drama) and White Palace (1990) in the role of Rachel. She also appeared in The Last Supper (1995). On December 6, 2004, Chagall appeared at the cast reunion for The Nanny, The Nanny Reunion: A Nosh to Remember.
