William H. Brodie initially spent some time in his father's business, but then entered the University of Aberdeen where he qualified as Bachelor of Medicine and Master of Surgery in 1880. After two years of post-graduate work at Edinburgh, Inverness and Dublin, he was awarded the degree Doctor of Medicine (MD) by the University of Aberdeen in 1882. Also in 1882 he married Rachel Paterson, with whom he eventually had a son and two daughters. That same year he and his wife emigrated to the Orange Free State (now the Free State) and settled in Philippolis. He was licensed to practise in the Cape Colony in March 1882. After seven years in Philippolis he moved to Johannesburg in 1889 and was licensed to practise in the South African Republic (Transvaal) in 1890. In 1896, following an unsuccessful attempt to overthrow the republic's government, he was jailed for some time as a member of the Reform Committee.
By 1898 Brodie was a member of the South African Medical Association. With W.G. Rogers and E.T.E. Hamilton he published 'A contribution to the pathology of infection by the pneumococcus' in The Lancet (1898).When the Anglo-Boer War broke out in 1899 he was in England on holiday. He joined the hospital ship Spartan as a civil surgeon, and on arrival in Durban was put in charge of another hospital ship, the Lismore Castle. Soon he was transferred to No. 6 General Hospital in Johannesburg, where he served during the remainder of the war. He was a strict disciplinarian and held strong opinions.
After the war Brodie was a Witwatersrand Mines Medical Officer and made measurements of the stature, weight, and chest dimensions of over 3000 adult male mineworkers who came from Tanzania, Malawi, Zambia, Zimbabwe, Mozambique, Botswana, and South Africa. This was among the earliest research in physical anthropology by a South African resident. His data were not published in his lifetime, but the measurements were continued by Dr. G.A. Turner*, who compiled and analysed the total data set. The work is valuable as a baseline against which to compare later measurements of the same populations in order to search for secular trends in adult stature.