Upon commissioning, the ship became the flagship of the 5th Cruiser Squadron of Home Fleet and was later transferred to the 2nd Cruiser Squadron as a private ship when the fleet reorganized in April 1909. She became the flagship of her squadron on 1 March 1910 and made a port visit to Torbay in January 1911. "Shannon" was relieved as flagship by the battlecruiser on 5 March 1912 and was transferred to the 3rd Cruiser Squadron as that squadron's flagship. In January 1914, she relieved "Indomitable" as flagship of the 2nd Cruiser Squadron during exercises off the northwest coast of Spain. The following month, "Shannon", together with the 1st Battlecruiser Squadron and the rest of the 2nd Cruiser Squadron, made a port visit to Brest, France.