George Stewardson Brady studied at the University of Durham College of Medicine. He qualified as a member of the Royal College of Surgeons of England, and as Doctor of Medicine and practised in Sunderland (just south of Newcastle-upon-Tyne) from 1857 to about 1890. In 1875 he was appointed as professor of natural history at Armstrong College, Newcastle-upon-Tyne, a post he held until his retirement in 1906.
In addition to his medical qualifications Brady also obtained the degree Doctor of Science (DSc). He was a fellow of the Royal Society of London, and a corresponding member of the Zoological Society of London. He joined the British Association for the Advancement of Science in 1863 and was still a member in 1905. His publications included reports on the Ostracoda and Copepoda (subclasses of the class Crustacea) of the Challenger Expedition of 1873-1876, the Copepoda of the British Isles (1878-1880), the marine and freshwater Copepoda of the North Atlantic and north-western Europe (1889), the Copepoda collected by the German Antarctic Expedition of 1901-1903, the Copepoda, Cladocera and Halocypridae of the Australian Antarctic Expedition of 1911-1914, and many papers on the same groups from all over the world. Many genera and species of these groups were named after him.
Brady's contributions to South African science included his papers 'On Entomostraca [a division of the class Crustacea] collected in Natal by Mr. James Gibson*' and 'On freshwater Entomostraca from various parts of South Africa', both published in the Annals of the Natal Museum (1907, Vol. 1, pp. 173-186 and 1913, Vol. 2, pp. 459-474), and three papers on the pelagic Entomostraca of Durban Bay, also collected by Gibson (Annals of the Durban Museum, 1914-1915, Vol. 1, pp. 1-9, 25-28, and 134-146).