Until the establishment of the Australian Academy of Science in 1954, the Royal Societies in each State were the principal homes of science in that State; national conferences were convened periodically by the Australasian (later Australian and New Zealand) Association for the Advancement of Science. Already an Associate Member of the Royal Society of Victoria, in 1917, just after he had arrived in South Australia, Fenner became a Fellow of the Royal Society of South Australia. He regularly attended its meetings, published in its Proceedings and took an active part in the deliberations of its Council. He was appointed Secretary in 1924, was a member of Council, 1925–27, Vice-President, 1928–29, President, 1930–31, Treasurer in 1932 and Honorary Editor of the Proceedings, 1933–37.