In 1899 he returned to South Africa, enlisting as a civil surgeon at the Yeomanry Hospital, Pretoria, during the Second Boer War.
After Mullins qualified as a doctor he returned to South Africa, working as a medical officer on the Rand, before settling in Grahamstown.
[2] In Grahamstown he set up in practice with a Dr. Drury, and at the same time took the role of medical officer St. Andrews College, his old school.
[4] With the outbreak of the First World War, Mullins again served his country, and was made a temporary Captain of the Royal Army Medical Corps in 1917.
[8] In 1896 Mullins was invited to return to South Africa, as part of the British Isles touring team.