Cormack was born on February 23, 1924 in Johannesburg, South Africa. During his early years, he attended the Rondebosch Boys' High School in Cape Town, and was a member of the debating and tennis teams. In 1944, Cormack received his B.Sc. in physics from the University of Cape Town and in 1945, he received his M.Sc. in crystallography in 1945 from the university. From 1947 to 1949, he attended University of Cambridge as a research student. While there, he met Barbara Seavey, an American physics student. Comack and Seavey would later get married. 