[1] The ship participated in the Italo-Turkish War of 1911–1912, during which time she supported the occupations of Benghazi and Derna, the island of Rhodes, and bombarded the fortifications defending the entrance to the Dardanelles.

During World War I, San Marco's activities were limited by the threat of Austro-Hungarian submarines, although the ship did participate in the bombardment of Durazzo, Albania in late 1918.

San Marco was captured by the Germans when they occupied northern Italy in 1943 and was found sunk at the end of the war.

[6] San Marco had a cruising range of 4,800 nautical miles (8,900 km; 5,500 mi) at a speed of 10 knots (19 km/h; 12 mph).

[5] The main armament of the San Giorgio-class ships consisted of four Cannone da 254/45 A Modello 1908 guns in twin-gun turrets fore and aft of the superstructure.

[5] When the Italo-Turkish War of 1911–1912 began on 29 September 1911, San Marco was not initially assigned to the 2nd Division of the 1st Squadron of the Mediterranean Fleet.

Of the many targets, Ancona was hardest hit, with disruptions to the town's gas, electric, and telephone service; the city's stockpiles of coal and oil were left in flames.

All of the Austrian ships safely returned to port, putting pressure on the Regia Marina to stop the attacks.

When the Austrians resumed bombardments on the Italian coast in mid-June, Admiral Paolo Thaon di Revel responded by sending San Marco and the other armoured cruisers at Brindisi—the navy's newest—to Venice to supplement the older ships already there.

[18] On 16 March 1924, she saluted King Victor Emmanuel III when he arrived in Fiume to attend the ceremony commemorating the city's annexation by Italy.

During a naval review for Adolf Hitler in the Bay of Naples on 5 May 1938, the ship was used as a target by the heavy cruisers Fiume and Zara.

[22] She was captured by the Germans when they occupied La Spezia on 9 September 1943; the ship was found at the end of the war sunk in the harbor there.