Arthur James Ballantine, son of Major Robert Ballantine and his wife Anna Letitia Maria Ballantine, passed the matriculation examination of the University of the Cape of Good Hope in 1904. He continued his studies at the South African College, Cape Town, in 1905 and in 1907 was awarded the degree Bachelor of Arts (BA) with honours in botany by the University of the Cape of Good Hope. Soon thereafter he wrote "A preliminary note on the embryo-sac of Protea lepidocarpon", which was published in the Annals of Botany (1909).
After graduating Ballantine went to Edinburgh to study medicine, qualifying as Bachelor of Medicine (MB) and Bachelor of Surgery (ChB) in 1912. Subsequently he worked for some time in England as house surgeon at the Leith General Hospital and Tunbridge Wells General Hospital. He was elected a Fellow of the Royal College of Surgeons of Edinburgh in 1914.
Returning to South Africa during World War I (1914-1918), Ballantine was appointed to a temporary post in the Department of Anatomy at the South African College in March 1915. However, at the end of that year he joined the Army Medical Corps. By 1926 he resided in Wynberg, Cape Town, and was honorary visiting physician to the Victoria Cottage Hospital there.
Ballantine was married three times, in 1920, 1931 and 1950.