After completion, the HMS Newfoundland (59) was assigned to the 10th Cruiser Squadron of the Home Fleet and then became the flagship of the 15th Cruiser Squadron in the Mediterranean, where she took part in the attack on Pantelleria in June 1943 and in the invasion of Sicily on month later.

In November 1944, she left Britain for the Pacific Ocean to join the Pacific Fleet, but an explosion in the port torpedo tubes in Alexandria delayed her journey. In May 1945, the cruiser was supporting the landings of the 6th Australian Division at Wewak, New Guinea and on 14 June was part of a Royal Navy Task Group that carried out sea and air strikes on the Japanese Naval Base of Truk, Caroline Islands. On 6 July, she left Manus in the Admiralty Islands to cover the British aircraft carriers, which attacked targets in the Tokyo area from 17 July on. Between 24 and 28 July, the attacks were concentrated on Kure to destroy the remains of the Japanese Fleet. After the Japanese surrender on 15 August, the cruiser landed a group of seamen and Royal Marines to take over the naval base at Yokosuka in the Tokyo Bay and was present when the Instrument of Surrender was signed aboard USS Missouri (BB 63) on 2 September.

Battle honours:
Mediterranean 1943
Sicily 1943
Japan 1945

After the war, the HMS Newfoundland (59) assisted in the repatriation of British and Commonwealth prisoners of war, eventually returned to Britain in December 1946, was placed in reserve and used as training ship before a refit at Plymouth in 1951. On 5 Nov 1952, she became flagship of the 4th Cruiser Squadron in the East Indies and also served in the Far East.
In 1956/57 the HMS Newfoundland (59) was in the Red Sea and Mediterranean, participating in the Suez war. On 1 Nov 1956, the cruiser encountered the Egyptian frigate Domiat during a patrol the Red Sea south of Suez and sank her by gunfire from a distance of 1500 yards, but the Egyptians bravely returned fire until their vessel capsized, hitting the cruiser with two 4in shells and wounding two men. 69 survivors from the frigate were picked up by the cruiser.
In January 1958, the ship arrived at Singapore and during August saw service in the Persian Gulf due to the revolution in which King Faisal was assassinated, returning to Singapore in September. On 2 November, the cruiser left the Far East and returned via the Seychelles, East and South Africa and Freetown to Portsmouth, where she was paid off on 24 Jun 1959.

On 30 Dec 1959, the HMS Newfoundland (59) was sold to Peru and renamed Almirante Grau. On 15 May 1973 renamed Captain Quinones and used as static training ship at Callao, finally sold for scrap in 1979 to Japan. 

At 13.37 hours on 23 July 1943, U-407 fired a spread of two torpedoes at a cruiser in a Task group of two cruisers and four destroyers off Syracuse and heard a detonation after 1 minute 10 seconds. HMS Newfoundland (59) (Capt W.R. Slayter, DSC, RN) was hit in the stern and lost her rudder, but managed to reach Malta, steering only by propellers. One rating was lost and six others were injured. After emergency repairs, she went to the Boston Navy Yard where she was repaired from August 1943 to April 1944. The ship then crossed the Atlantic to the Clyde for a long refit until November 1944.

For some time it was thought that the Italian submarine Ascianghi had torpedoed HMS Newfoundland (59), before she was herself sunk 10 miles off Augusta. The Italian survivors reported that they had fired two torpedoes at a cruiser, but this attack was very likely directed against HMS Laforey (G 99) (Capt R.M.J. Hutton, DSO, RN), which evaded a torpedo at 15.41 hours and then sank the Italian submarine together with HMS Eclipse (H 08) (Cdr E. Mack, DSO, DSC, RN) at 16.32 hours.