After commissioning, Ossosy joined the 11th Destroyer Flotilla of the Grand Fleet. Ossory was refitting in April 1916, but following the outbreak of the Easter Rising against British rule in Ireland on 24 April 1916, was employed in escorting transports carrying two infantry brigades from Liverpool to Ireland to reinforce British forces. She took part in the Battle of Jutland on 31 May – 1 June 1916, still part of the 11th Destroyer Flotilla. On 10 December 1916, Ossory, was one of three destroyers that were attached to the 4th Light Cruiser Squadron, and sent to patrol between Shetland and Norway in an attempt to intercept the German liner , which was about to leave safe harbour in Tromsø to return to Germany. Prinz Friedrich Wilhelm successfully escaped the British ships.
