Langton was born in Boston, Massachusetts. She studied astronomy at Wellesley College and the University of Michigan, receiving a bachelor's degree in 1944. She received an M.A. in art history from the University of Michigan in 1945, and another M.A. from Radcliffe College in 1948. She studied at the Boston Museum School from 1958 to 1959.
In 1961 Langton wrote and illustrated her first book for children, The Majesty of Grace, a story about a young girl during the Depression who is certain she will some day be Queen of England. Langton has since written a children's series, The Hall Family Chronicles, and the Homer Kelly murder mystery novels. She has also written several stand-alone novels and picture books.
Langton's novel The Fledgling is a Newbery Honor book.