At the age of 14, Weaver began using the name "Sigourney", taking it from a minor character in "The Great Gatsby". She briefly attended the Brearley School and Chapin School in New York before arriving at the Ethel Walker School (Walker's) in Simsbury, Connecticut, where she developed an early interest in performance art. One of her early roles was in a school adaptation of the poem "The Highwayman", and on another occasion she played a Rudolph Valentino character in an adaptation of "The Sheik". She was also involved in theatrical productions of "A Streetcar Named Desire" and "You Can't Take It with You" during one summer at Southbury, Connecticut. Weaver reportedly reached the height of by the age of 11, which had a negative impact on her self-esteem. She recalled feeling like "a giant spider" and never having "the confidence to ever think I could act."