 Along with other members of the Chelsea Arts Club, including Tom Roberts, he joined the Royal Army Medical Corps (British Army) at the age of 48.He worked at the 3rd London General Hospital in Wandsworth and reached the rank of corporal.Streeton was made an Australian Official War Artist with the Australian Imperial Force, holding the rank of Honorary Lieutenant, and he travelled to France on 14 May 1918 and was attached to the 2nd Division, receiving his movement order on 8 May 1918.