In February 1915, "Canopus" transferred to the Mediterranean to take part in the Dardanelles campaign. On 2 March 1915, she took part in the second attack on the Ottoman Turkish entrance forts at the Dardanelles. During this operation, she led the 4th Sub-Division, which also included the pre-dreadnoughts and . "Canopus" and "Swiftsure" were tasked with suppressing the guns in the fortress at Dardanus while "Cornwallis" would engage minor batteries at Intepe and Erenköy. "Canopus" and "Swiftsure" entered the straits at 13:20 and closed to within of the north shore, where at 14:20 they opened fire at the fortress on the other side of the straits, some away. The ships fired for about two hours before the Ottomans inside Dardanus returned fire at 16:15, which they did quite accurately, straddling "Canopus" quickly and scoring a hit on her quarterdeck that damaged a wardroom. A second shell knocked down her topmast and a third holed her after funnel, exploded, and rained fragments on two of her boats.