On commissioning, "Porpoise" joined her sister ships in the 4th Destroyer Flotilla, based at Portsmouth. On the outbreak of the First World War, the 4th Flotilla, including "Porpoise", became part of the Grand Fleet. On 23 December 1915, "Porpoise" and the destroyer were escorting a Russian icebreaker when forced to hove to near Fair Isle in a heavy gale. On 24 December, the 1st Cruiser Squadron, on patrol in the North Sea were ordered to search for the two destroyers, and the cruisers and left Scapa Flow to join in the search. "Porpoise" reached the shelter of the Cromarty Firth on 25 December, with "Morning Star" following on 26 December, both destroyers having suffered extensive weather damage and flooding. She was under refit on 24 April 1916, and so did not take part in the Grand Fleet's sortie in response to the German Bombardment of Yarmouth and Lowestoft.