FitzGerald worked as a land agent in Ireland for seven years, and from 1895 until 1918 was a member of the London Stock Exchange, with the firm of Basil Montgomery FitzGerald and Co.
He was appointed a second-lieutenant in the West Somerset Yeomanry on 18 January 1900. Following the outbreak of the Second Boer War in late 1899, he had volunteered for active service and was attached as a lieutenant to the 25th Company of the 7th Battalion, Imperial Yeomanry, on 24 February 1900.[2] The company left the United Kingdom for South Africa in the SS Mahratta in early March 1900.[3] After arrival, FitzGerald served with the company, and later as ADC to General French, for which he was mentioned in despatches and awarded the Queen's Medal with six clasps. He also served during the European War as private secretary to French in 1914, for which he was awarded the CB (in 1916), the Legion d'Honneur and the Order of Leopold.[1]