[3] Upon completion, Viscount was assigned to the Grand Fleet, based at Scapa Flow in the Orkney Islands, in which she served for the rest of World War I.

[2] Viscount rapidly gained a reputation as an exceptionally fast ship and successfully attacked and sank at least one German U-boat which was caught on the surface.

[3] In 1921 she joined the light cruisers Caledon, Castor, Cordelia, and Curacoa and the destroyers Vanquisher, Vectis, Venetia, Viceroy, Violent, Winchelsea, and Wolfhound in a Baltic Sea cruise, departing the United Kingdom on 31 August 1921.

The ships crossed the North Sea and transited the Kaiser Wilhelm Canal to enter the Baltic, where they called at Danzig in the Free City of Danzig; Memel in the Klaipėda Region; Liepāja, Latvia; Riga, Latvia; Tallinn, Estonia; Helsinki, Finland; Stockholm, Sweden; Copenhagen, Denmark; Gothenburg, Sweden; and Kristiania, Norway, before crossing the North Sea and ending the voyage at Port Edgar, Scotland, on 15 October 1921.

[3] When the United Kingdom entered World War II on 3 September 1939, Viscount was deployed with the 19th Destroyer Flotilla, based at Plymouth, for convoy escort and patrol duty in the English Channel and Southwestern Approaches.

On 8 April 1940, Viscount, the destroyers Vimy and Witch, and the Shoreham-class sloop Rochester relieved a French warship as the escort of Convoy HG 25F for the last leg of its voyage from Gibraltar to Liverpool; although Vimy and Witch detached the next day, Viscount and Rochester stayed with the convoy until arrived at Liverpool on 11 April 1940.

On 17 May 1940, she joined the destroyers Diana and Veteran in escorting the aircraft carrier HMS Glorious from the River Clyde in Scotland to the Norwegian coast.

Later that day, the destroyers rendezvoused with the troopships – carrying Allied personnel evacuated from Norway as the campaign there ended in the German conquest of the country – and the repair ship Vindictive and took them under escort to the Clyde.

Detaching from HG 47, she rendezvoused with Convoy HX 90 – 41 ships bound from Halifax, Nova Scotia, Canada, to Liverpool – as its escort on 1 December 1940.

With the conversion complete, she underwent post-conversion acceptance trials and, having passed them, performed work-ups in December 1941 to prepare for her return to convoy duty, which she did later that month.

[3] In March 1942, Viscount was "adopted" by the civilian community of Chislehurst and Sidcup in Kent in a Warship Week national savings campaign.

[3] In October 1942, Viscount was part of the escort of Convoy SC 1 CW, which came under attack by 10 German submarines of the "Wotan" (Wōden) group.

In order to free up her crew members to man newer, more modern escort ships, she was withdrawn from operations in February 1945 and decommissioned in March 1945.