In April 1919, "Curacoa" joined the 1st Light Cruiser Squadron of the newly established Atlantic Fleet. The following month, however, she was deployed to the Baltic as part of the British intervention in the Russian Civil War in support of the White Russians against the Bolsheviks. On 7 May, Rear-Admiral Walter Cowan transferred his flag to the ship from her half-sister . Ten days later, the ship was en route from Helsinki to Liepāja when she struck a mine with her stern, east of Reval (now Tallinn). One crewman was killed and three injured by the explosion. Cowan, who was taking a bath at the time, was dumped out of the bath, running to the bridge dressed only in an overcoat until clothing could be brought up from his "day cabin". "Curacoa" was able to reach a speed of after some repairs and reached Reval later that day. After temporary repairs there, she returned to the UK for permanent repairs at Sheerness Dockyard; her rudder fell off while passing The Skaw and the ship could only be steered with her engines for the last to the dockyard.