Dalrymple-Hay entered the Royal Navy in 1834. During his naval career he was involved in the Sixth Xhosa War in South Africa and the Oriental Crisis in Syria, being present when Beirut and St Jean d'Acre fell. He was also concerned with successful operations against Chinese pirates in the 1840s. He commanded HMS "Victory" from 1854 and then commanded HMS "Hannibal" during the Crimean War and was decorated by the British and Turkish governments. He was promoted to captain in 1850 and commanded HMS "Indus" from 1856. He was promoted to rear admiral in 1866, before retiring as an admiral in March 1878. He was Fourth Naval Lord from 1866 to 1868.