He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow. In 1893 he married Mary Baird Baillie.
From 1903 to 1910 he was Professor of Zoology and Geology at Victoria College, Stellenbosch, South Africa, and subsequently he became keeper of vertebrate paleontology at the South African Museum, Cape Town.
Broom was first known for his study of mammal-like reptiles. After Raymond Dart's discovery of the Taung Child, an infant australopithecine, Broom's interest in paleoanthropology was heightened. Broom's career seemed over and he was sinking into poverty, when Dart wrote to Jan Smuts about the situation. Smuts put pressure on the South African government, and managed to get a position for Broom. In 1934 he joined the staff of the Transvaal Museum in Pretoria as Assistant in Palaeontology.
In the following years, he and John T. Robinson made a series of spectacular finds, including fragments from six hominids in Sterkfontein, which they named Plesianthropus transvaalensis, but which was later classified as an adult Australopithecus africanus, as well as more discoveries at sites in Kromdraai and Swartkrans.
The remainder of Broom's career was devoted to the exploration of these sites and the interpretation of the many early hominid remains discovered there. For his volume, The South Africa fossil ape-men, the Australopithecinae, in which he proposed the Australopithecinae subfamily, Broom was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences in 1946. He continued to write to the very last. Shortly before his death he finished a monograph on the Australopithecines and remarked to his nephew:
- "Now that's finished ... and so am I".
- Broom R. 1930. The origin of the human skeleton: an introduction to human osteology. Witherby, London.
- Broom R. 1932. The mammal-like reptiles of South Africa, and the origin of mammals. Witherby, London.
- Broom R. 1946. The South Africa fossil ape-men, the Australopithecinae.
- Broom, R. 1950. Finding the missing link. Watts, London.
- Findlay, George H. 1972. Robert Broom F.R.S. Palaeontologist & Physician 1866-1951: biography / appreciation /bibliography. Cape Town: A. A. Balkema. ISBN 8696-10181-2
- D.M.S. Watson 1952. "Robert Broom. 1866-1951" Obituary Notices of Fellows of the Royal Society. 8, #21 pp. 36-70.
- "Daniel Giraud Elliot Medal". National Academy of Sciences. http://www.nasonline.org/site/PageServer?pagename=AWARDS_elliot. Retrieved 15 February 2011.
- Virginia Morell, Ancestral passions, Chapter 13.