Thomas Perry was recommended to the government of the Cape Colony by the British secretary of state in 1820 and arrived in the colony soon afterwards. He was registered as surgeon, apothecary and accoucheur in the Cape Colony on 13 April 1821, though it seems that he had no formal medical qualifications. By 1822 he was officially recognised as surgeon at Graaff Reinet, and by 1826 as surgeon of the sub-district Beaufort. In 1828 he was appointed district surgeon of Graaff Reinet, being one of the first batch of ten district surgeons appointed in the colony that year (Burrows, 1958). However, in the African court calendar he was already listed as district surgeon from 1823 onwards. By 1829 he was furthermore also deputy sheriff of Graaff Reinet. On 8 March 1822 he married Maria E. Muller with whom he had seven children.
In 1831 a smallpox epidemic started among the Griquas in Philippolis and spread like wild-fire among the unvaccinated tribe. It was a severe form of the disease, with a mortality of 80% or more. Perry and Dr John Atherstone* went to the town to vaccinate the people and the epidemic did not affect the rest of the colony.
For some years before 1830 Perry had made observations on horse sickness, to which he referred as "this deadly lung inflamation". During 1830 he wrote to the Governor describing the symptoms of the disease both before and after death, and discussed its possible cure. The Governor thanked him for his work and referred the report to the Colonial Medical Committee for possible publication. The paper was published under Perry's name with the title "On the horse sickness" in the July-September 1830 issue of the South African Quarterly Journal (Vol. 1(4), pp. 438-442).