At the outbreak of First World War, Patey commanded the Australian naval squadron as part of the New Zealand Samoa Expeditionary Force that captured German Samoa and the Australian Naval and Military Expeditionary Force that captured German New Guinea. He sailed with HMAS "Australia" to join the 2nd Battlecruiser Squadron at Rosyth, Scotland and on 8 February 1915, "Australia" became the flagship of the squadron. Patey was appointed Commander-in-Chief, North America and West Indies Station from March 1915.