She was transferred to the Home Fleet in December 1939, although she was badly damaged in a collision the following month, and required repairs that lasted until July 1940.

Duncan rejoined the 13th Destroyer Flotilla at Gibraltar in July and escorted several convoys to Malta during the rest of the year.

After a refit, she briefly returned to the 13th Destroyer Flotilla before joining the Eastern Fleet in the Indian Ocean to participate in Operation Ironclad in May 1942.

At that time she was transferred to coastal anti-submarine patrols to counter any last-gasp effort by the Kriegsmarine to interfere with the Allied supply lines to the Continent.

Duncan carried a maximum of 390 long tons (400 t) of fuel oil that gave her a range of 5,870 nautical miles (10,870 km; 6,760 mi) at 15 knots (28 km/h; 17 mph).

Built as a flotilla leader, she displaced 25 long tons more than the rest of her class and carried an extra 30 personnel.

[4] The ship was initially assigned as the leader of the 1st Destroyer Flotilla in the Mediterranean and made a brief deployment to the Persian Gulf and Red Sea in September–November 1933.

After refitting at Portsmouth between 3 September and 23 October, Duncan led most of her flotilla to the China Station, arriving at Hong Kong on 3 January 1935.

On 28 October 1938, Duncan was struck by the Greek steamer Pipina whilst lying at anchor at Foo Chow, China.

[5] With the outbreak of war, Duncan and her sisters Diana, Daring, and Dainty, were transferred to the Mediterranean Fleet, arriving at Alexandria on 30 September.

During the morning of 10 December, Barham collided with Duchess off the Mull of Kintyre in heavy fog, sinking the destroyer with the loss of 124 lives.

[6] She was damaged in a collision with a merchant vessel on 17 January whilst escorting Convoy ON18, causing a twenty-foot hole in her side but fortunately she did not sink and was taken under tow.

[11] In October she was assigned as part of the escort for Convoy HG 75, from Gibraltar to Liverpool,[12] because she was scheduled for a refit in the Sheerness Dockyard.

[14] The following month, Duncan was transferred to the 22nd Destroyer Flotilla of the Eastern Fleet to support Operation Ironclad, the invasion of Diego Suarez.

[13] By this time the ship was in poor shape and required an extensive refit; the work last from 12 November to 17 May 1944 at the North Woolwich, London shipyard of Harland and Wolff.