Dunbar was taught by private tutors and at private schools. Her education began at Laboratory School in Chicago. She graduated from Bryn Mawr with a B.A. (dual major in mathematics and psychology) in 1923. She received a Med. Sci D degree from Columbia University in 1935. Dunbar focused on medieval literature and Dante, which impacted her medical practice and therapeutic approaches. While at Columbia University, Dunbar was simultaneously enrolled at Union Theological Seminary. In 1927, Dunbar graduated from Union Theological Seminary, with a degree in theology, and completed her first year at Yale University's Medical School.