 Upon completion in September 1911, "Falmouth" was assigned to the 2nd Battle Squadron of the Atlantic Fleet and was transferred to the reserve 2nd Light Cruiser Squadron of the Second Fleet at The Nore on 30 June 1913.By the end of the year, the ship had been transferred to the 5th Cruiser Squadron, also of the Second Fleet.On the outbreak of the First World War in August 1914, she was assigned to the 1st Light Cruiser Squadron of the Grand Fleet.