Tamblyn was born in Santa Monica, California, the daughter of Russ Tamblyn, an actor, dancer, and singer, and Bonnie Murray, a singer, teacher, and artist. Debord, was attending as a family friend and ended up convincing her father to allow Tamblyn to go on auditions. Tamblyn became well known for playing Joan Girardi, a teenage girl who receives frequent visits from God on the CBS drama series Joan of Arcadia. Tamblyn's father made several appearances as God in the form of a dog walker on the show, which ran from 2003 to 2005. In 2005, Simon & Schuster Children's Publishing published a book of poems that she wrote over the span of seven years entitled Free Stallion.