Dorling served in South Africa throughout the Second Boer War from 1899 to 1902. He was Field Paymaster to the Natal Field Force, which took part in the effort to Relieve Ladysmith, and he was thus present at the battles of Colenso (December 1899) and the Tugela Heights (February 1900). Promoted to major on 23 March 1900, he stayed in South Africa until after the war ended in June 1902, leaving for England on the SS "Dunvegan Castle" in October that year. For his service he was Mentioned in Despatches (London Gazette 29/07/1902), received the Queen’s Medal with 5 clasps and the King’s Medal with 2 clasps, and was awarded the Distinguished Service Order (DSO) in the October 1902 South Africa Honours list (the award was dated 22 August 1902).