Barbara Gittings was born to Elizabeth (née Brooks) Gittings and John Sterett Gittings in Vienna, Austria, where her father was serving as a U.S. diplomat. Barbara and her siblings attended Catholic schools in Montreal. She was so immersed in Catholicism at one point in her childhood that she considered becoming a nun. Her family returned to the United States at the outbreak of World War II and settled in Wilmington, Delaware. Although aware of her attraction to other girls, Gittings said she first heard the word "homosexual" when she was rejected for membership in the National Honor Society in high school. Despite being an excellent student, a teacher who had reservations about her character took her aside and told her that the rejection was based on what the teacher believed were "homosexual inclinations".