The ship was assigned to the Channel Fleet after the beginning of the First World War in August 1914 and ferried Royal Marines to Belgium that same month. In early 1915, she was ordered to the Mediterranean to support Allied forces in the Dardanelles Campaign, but "Prince of Wales" only remained there briefly before being ordered to the Adriatic to reinforce Italian forces there in case of an attack by the Austro-Hungarian Navy. The ship was ordered home in early 1917 and reduced to reserve upon her arrival. "Prince of Wales" served as an accommodation ship until she was listed for sale in late 1919. The ship was sold for scrap in mid-1920 and broken up thereafter.