After long service on the Australia Station with the Royal Navy, HMS Encounter was lent to the RAN as a training cruiser, pending the completion of HMAS Brisbane. She was commissioned into the RAN on 1 July 1912. On 4 October 1913 she entered Sydney Harbour as part of the Australian Fleet Unit.
Following the outbreak of the First World War in August 1914, Encounter was part of the force which occupied German New Guinea. In the course of these operations she captured the steamer Zambezi on 12 August and, on 14 September, bombarded Toma Ridge to support the Australian Military and Naval Expeditionary Force. She covered the landing at Madang on 24 December.
In October, Encounter patrolled the Fiji-Samoa area, capturing the German schooner Elfrede. After a refit, she continued patrol duties in the Pacific, landing troops to protect the cable station on Fanning Island in July 1915. After grounding on a coral reef at Johnson Island, Encounter had to put-in at Hong Kong for repairs.
From January 1916, Encounter patrolled East Indies waters, returning to Australia the next month. She remained in Australian waters for the rest of the war. During this period she attended to the stricken Cumberland, which had struck a mine off Gabo Island on 6 July 1917, and searched the wreck of the raider Seeadler at Mopelia Island in September 1917.
After the war, Encounter served as training ship, and, from 1923, disarmed and renamed Penguin, as an accommodation vessel. In 1932 her hulk was scuttled off Bondi.