After commissioning, "Red Deer" was assigned to the Western Local Escort Force as a convoy escort. At various periods after that she served with Sydney Force, Halifax Local Defence Force and the Gulf Escort Force, as part of the Battle of the St. Lawrence. On 12 January 1942 she rescued 95 survivors from the British merchant ship SS "Cyclops", which had been torpedoed by . Beginning in February 1944, "Red Deer" was assigned to Newfoundland Force. In May 1944 she began a refit at Liverpool, completing it in July 1944 and working up in Bermuda later that month. She returned to Newfoundland Force after working up and remained with the unit until the end of the war. She was paid off at Halifax, Nova Scotia on 30 October 1945 and laid up at Shelburne.