Commissioned at Montreal on November 28, 1940, she arrived at Halifax on December 11 to work up and complete stores. On February 9, 1941, Mayflower left with convoy HX.108 for the U.K., fitted, like her sister Hepatica, with a dummy gun. This and other shortcomings were look after on the Tyne River, where she was pronounced complete on May 5, and she left Loch Ewe as a member of EG 4 with convoy OB.332 for Iceland on June 10. Later that month she joined Newfoundland Command, and for the remainder of the year served between Iceland at St. John's as an ocean escort. During this period she took part in the battle of convoy SC.44, when four merchant ships and HMCS Levis were lost, Mayflower taking off survivors of the latter. After a major refit at Charleston, S.C., from December 9, 1941 to February 9, 1942, Mayflower resumed her mid-ocean role on the "Newfie-Derry" run until April, 1944. In April, 1942, she became a member of EG A-3, transferring to C-3 in February, 1943. She underwent two further long refits: from October 29, 1942 to January 11, 1943, at Pictou; and from November 29, 1943 to February 14, 1944, at Norfolk, Va. She received her extended fo'c's'le during the latter, following which she worked up in St. Margaret's Bay, then sailed on April 21 for the U.K. to join Western Approaches Command, Greenock, for invasion duties. She left Oban on may 31, to escort blockships for Normandy and arrived off the beaches on the day after D-Day. For the remainder of the war she operated in U.K. waters, and on May 31, 1945, was paid off for return to the RN. Laid up at Grangemouth, Scotland, she was broken up at Inverkeithing in 1949.
Focsle Extended, Baltimore, MD, 14 Feb 44