At the start of World War I, "Warrego" was assigned to the Australian force tasked with neutralising German colonies in the region, along with finding and destroying the German East Asia Squadron. She was involved in the capture of Rabaul and the Battle of Bita Paka during 1914. After patrol work in Australian, New Guinea, and South-east Asian waters, "Warrego" and her sister ship were assigned to the Mediterranean in 1917, and served as an anti-submarine patrol force. The ship participated in the Second Battle of Durazzo in 1918. After the war's end, "Warrego" returned to Australia, and was placed in reserve.