The ship was assigned to the 1st and 4th Light Cruiser Squadrons (LCS) of the Grand Fleet for the entire war and played a minor role in the Battle of Jutland in mid-1916.

The C-class cruisers were intended to escort the fleet and defend it against enemy destroyers attempting to close within torpedo range.

The ships carried enough fuel oil to give them a range of 3,680 nautical miles (6,820 km; 4,230 mi) at 18 knots (33 km/h; 21 mph).

All of these changes adversely affected the ship's stability and the additional 21-inch torpedo tubes and the aft control position were removed by the end of 1921.

[6] Commissioned into service in the Royal Navy that same month, Cordelia was assigned to the 1st Light Cruiser Squadron (LCS) of the Grand Fleet.

[10] In early August 1914, Cordelia and the rest of her squadron were among the ships dispatched to hunt for the German commerce raider SMS Meteor, which was trying to return to Germany.

Cordelia fired four rounds from her main armament at the light cruiser Elbing, but they fell short of the target.

[15] By 1 May 1919, however, she had been assigned to the Devonport Gunnery School,[16] and by 18 January 1920 she had recommissioned for service in the 2nd Light Cruiser Squadron in the Atlantic Fleet.

[18] In 1921, Cordelia joined the light cruisers Caledon, Castor, and Curacoa and the destroyers Vanquisher, Vectis, Venetia, Viceroy, Violent, Viscount, Winchelsea, and Wolfhound in a Baltic cruise, departing British waters on 1 September.

The ships crossed the North Sea and transited the Kaiser Wilhelm Canal to enter the Baltic Sea, where they called at Danzig in the Free City of Danzig; Memel in the Klaipėda Region; Liepāja and Riga, Latvia; Tallinn, Estonia; Helsinki, Finland; Stockholm, Sweden; Copenhagen, Denmark; Gothenburg, Sweden; and Kristiania, Norway.