The first three destroyers were operating with the Australian fleet at the start of World War I. The three ships were assigned to the Australian Naval and Military Expeditionary Force, and participated in the capture of German New Guinea. After the conclusion of the campaign, the destroyers were assigned to home waters for a short period, then assigned to Malayan and surrounding waters until late 1916. During August and September, the second group of River-class destroyers began relieving the ships of the first group from Malayan patrols, with "Parramatta", "Yarra", and "Warrego" returning to Australia.