After commissioning she was worked up on the
River Clyde in
Scotland. She sailed to join the 4th Cruiser Squadron in the
Pacific Theatre, but was too late to see active service, although she was employed in the operations at
Hong Kong,
Manila and in Japan. She returned home for refit, arriving at
Esquimalt, British Columbia on 27 November 1945. In January 1949,
Ontario took part in the largest training cruise by the Royal Canadian Navy to that date which included the
aircraft carrier , the destroyers ,
Athabaskan and the frigate
Antigonish. The group, designated CTF 215, participated in naval exercises with US and British vessels in the Caribbean Sea. In February 1951,
Ontario sailed to Australia, taking part in joint naval exercises with the
Royal Australian Navy. On the way the ship made several port visits, returning to Canada in June. In October 1951,
Ontario sailed to the east coast where after arrival, Princess
Elizabeth and Prince Philip, Duke of Edinburgh sailed on the cruiser from
Sydney, Nova Scotia, through the Cabot Strait to Newfoundland during the Royal Visit. The ship returned to Esquimalt following the tour, arriving in December. From September to December 1952,
Ontario sailed around South America on a training cruise, making several port visits. While entering the harbour at
Buenos Aires, the cruiser was overtaken by the merchant vessel and struck amidships. The ship continued on her cruise until arriving at
Rio de Janeiro on 6 November. There it was found that the starboard propellers were damaged. The outer propeller was removed and repairs were made to the inner one. After nearly two weeks at Rio de Janeiro,
Ontario was forced to return to Esquimalt at a reduced speed. On 15 June 1953 the cruiser took part in the
Fleet Review to celebrate the
Coronation of Queen Elizabeth II. In January 1954,
Ontario began a training cruise across the Pacific, visiting Australia, New Zealand and
Tonga before returning to Esquimalt in April.
Ontario performed a three-month training cruise to Australia and New Zealand in early 1955, returning to Canada on 2 April. The cruiser then departed on 25 April for a four-month cruise of Europe. In June 1956
Ontario departed Esquimalt for a two-month summer training cruise along the coasts of North and South America, going as far south as Ecuador. The cruiser returned to port on 10 August after meeting the
Second Canadian Escort Squadron off the coast of
California.
Ontario was
paid off on 15 October 1958. She arrived at
Osaka for breaking up on 19 November 1960. ==Ship's bell==