When World War II began in September 1939, "Gallant" was in the Mediterranean, but she and her entire flotilla were transferred to the Western Approaches Command at Plymouth in October. After a boiler cleaning, the ship was reassigned at the end of the month to the Nore Command in Harwich for patrol and escort duties. On 2 February 1940 "Gallant" and her sister ship, , rescued the crew from the oil tanker "British Councillor" which was sinking after it had struck a mine. "Gallant" took over escorting Convoy HN 12 after the destroyer was sunk on 18 February and she rescued 12 survivors from the Swedish ship "Santos" near Duncansby Head a week later. On 20 March 1940 she escorted the armed merchant cruisers "Cilicia" and after they collided. The ship was refitted at Southampton between 28 March and 30 April and rejoined her flotilla at Harwich the next day. During the evening of 9/10 May, "Gallant" and the destroyer rescued most of the crew of the destroyer after the latter ship was torpedoed by a German E-boat in the North Sea.