"Curacoa" was ordered in March–April 1916 as part of the Repeat War Programme. She was the fourth ship of her name to serve in the Royal Navy and named to commemorate the capture of the Dutch island of Curaçao in 1807. The ship was laid down at Pembroke Royal Dockyard on 13 July. She was launched on 5 May 1917 and completed on 18 February 1918. Her first commander was Captain Barry Domvile. On commissioning, "Curacoa" became flagship of the 5th Light Cruiser Squadron, part of the Harwich Force, serving there for the rest of the war. In association with John Cyril Porte's birthday and a medal ceremony at RNAS Felixstowe, her crew was inspected by King George V at Harwich on 26 February. From June onwards, she participated in reconnaissance sweeps ordered by Rear-Admiral Reginald Tyrwhitt, commander of the Harwich Force. Sometime in 1918, a pair of 2-pounder (40 mm) Mk II "pom-pom" light AA guns were installed.