In February 1882 Ardagh was appointed instructor in military history, law, and tactics at the School of Military Engineering at Chatham, but on 5 July he was sent to Egypt, where he was occupied almost continuously for the next four years. His first duty was to place Alexandria in a state of defence after its bombardment by the British fleet and to take charge of the intelligence department there. Ardagh was employed in the railway administration at Ismailia, and was present at the actions at Kassassin and Tel-el-Mahuta, and at the battle of Tel-el-Kebir in September 1882. On 17 November 1882 he was appointed Deputy Assistant-Adjutant and Quartermaster-General, and was promoted to brevet lieutenant-colonel on 18 November 1882. He was mentioned in Lord Wolseley's despatch at the end of the campaign, and also received the British war medal with clasp for Tel-el-Kebir, the Khedive's bronze star, and the fourth class of the order of the Osmanieh.