When World War II began in September 1939, "Grenade" was in Alexandria, but she, and her entire flotilla, was transferred to the Western Approaches Command at Plymouth in October. On 7 November she collided with her flotilla leader, and her repairs were not completed until 9 December. During the next several months she was assigned to contraband control duties in the Downs. She, and her sister ship, , rescued 117 survivors from "Grenville" after the latter ship struck a mine on 19 January 1940. The ship was refitted in London between 27 January and 27 February, but was struck by the ocean liner on 27 February and was only temporarily repaired there. "Grenade" received permanent repairs in Harwich from 2 March to 3 April and was assigned to Home Fleet at Scapa Flow after their completion.