Helen Dean Fish was born in Hempstead, Long Island. In 1912 she graduated from Wellesley College in Massachusetts. After graduating, she taught at the Asheville Home School for Girls in Asheville, North Carolina. In 1914 she studied playwriting at Radcliffe College in Massachusetts. In 1915 she moved to New York City and began working with drama clubs. In 1917 she became a manuscript reader at the Frederick A. Stokes Co., and in 1922 she was appointed their first children's book editor. She remained in that position when Stokes was merged with J. B. Lippincott in 1941, and she continued in it until her death at age 64.
In 1937, she published Animals of the Bible, a collection of Bible verses selected by her and illustrated by Dorothy Lathrop, which won the first Caldecott Medal ever awarded. She wrote several children's books and one book for adults.
