The Royal Canadian Navy (RCN) was assigned responsibility for anti-submarine warfare (ASW) and controlling sea space in the western North Atlantic.

They were built to counter nuclear, biological and chemical attack conditions, which led to a design with a rounded hull, a continuous main deck, and the addition of a pre-wetting system to wash away contaminants.

As with the British Type 12 design, the provision for long-range homing torpedoes (in this case BIDDER [Mk 20E] or the US Mark 35) were included.

[8] Following successful trials aboard the frigate Buckingham and sister ship Ottawa, plans to convert the St. Laurent class took shape.

The ship was commissioned at Sorel into the Royal Canadian Navy on 16 August 1956 and initially carried the hull number DDE 234 as a destroyer escort.

From October to November 1956, Assiniboine sailed with the First Canadian Escort Squadron to northern Europe, making a series of port visits.

[16] In January 1959, she transferred to the west coast and in July, carried Queen Elizabeth II and Prince Philip from Vancouver to Nanaimo.

[16] In 1974, Assiniboine was anchored in Lisbon, Portugal as part of the NATO Standing Naval Force Atlantic, with crew ashore, when the Carnation Revolution occurred.

[5][19] Assiniboine was selected by the Canadian Forces for the Destroyer Life Extension (DELEX) program beginning on 23 April 1979 and completed this refit on 16 November.

[5][16] On 2 July 1981, Assiniboine ran aground in Halifax Harbour in heavy fog, requiring the aid from several tugboats to get free.

[20] In 1984, while acting as an escort for the Tall Ships race, she was part of the search for the crew of the lost sailing vessel Marques.

[16] She was decommissioned from active service in the Canadian Forces on 14 December 1988 and was used as a harbour training ship at CFB Halifax beginning on 3 January 1989.