FitzGerald saw service in the Second Boer War, being mentioned in despatches four times and awarded the Distinguished Service Order in 1901. His Queen's South Africa Medal had four clasps: Belfast, Orange Free State, Defence of Ladysmith, Laing's Nek. While still in South Africa, he was appointed adjutant of his regiment on 6 May 1902. Following the war, in December 1903, FitGerald became the Aide-de-Camp to Brigadier General Michael Rimington, commanding the 3rd Cavalry Brigade. Then, in January 1905, he was promoted to captain. By 1913, FitzGerald had been promoted to major and was holding the position of a Brigade Major, Staff Officer at the War Office.