During the early part of the destroyer's career, "Warrego" operated in Australian waters. 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. On the night of 11 August 1914, "Warrego" and sister ship were tasked with entering Simpson Harbour at Rabaul to find and lure the German ships into the guns of the battlecruiser , but found no ships in harbour. During late August and early September, the destroyer escorted the Australian Naval and Military Expeditionary Force to New Britain, and was involved in the landing of troops at Kabakaul to capture a nearby wireless station. Apart from a brief docking in Sydney, "Warrego" remained in the New Guinea area until 5 February 1915, when she was reassigned to patrols along the east coast of Australia. In October, she sailed to Borneo, and carried out patrols in the region until August 1916.