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.

[3] In October 1948, Ontario was joined by the destroyers Cayuga, Athabaskan, Crescent and the frigate Antigonish in sailing to Pearl Harbor, Hawaii; the largest deployment of the Royal Canadian Navy following the war.

[4] In January 1949, Ontario took part in the largest training cruise by the Royal Canadian Navy to that date which included the aircraft carrier Magnificent, the destroyers Haida, Athabaskan and the frigate Antigonish.

[5][6] In February 1951, Ontario sailed to Australia, taking part in joint naval exercises with the Royal Australian Navy.

[8] From September to December 1952, Ontario sailed around South America on a training cruise, making several port visits.

[9] While entering the harbour at Buenos Aires, the cruiser was overtaken by the merchant vessel SS Arauco and struck amidships.

[11][12] In January 1954, Ontario began a training cruise across the Pacific, visiting Australia, New Zealand and Tonga before returning to Esquimalt in April.