For most of World War I, "Erzherzog Karl" remained in her home port of Pula, in present-day Croatia, except for four engagements. In 1914, she formed part of the Austro-Hungarian flotilla sent to protect the escape of the German ships SMS "Goeben" and SMS "Breslau" from the British-held Mediterranean; she advanced as far as Brindisi before being recalled to her home port. Her sole combat engagement occurred in late May 1915, when she participated in the bombardment of the Italian port city of Ancona. She also took part in suppressing a major mutiny among the crew members of several armored cruisers stationed in Cattaro between 1–3 February 1918. She also attempted to break through the Otranto Barrage in June of that year, but had to retreat when the dreadnought was sunk. After the war, "Erzherzog Karl" was awarded to the French as a war prize, but ran aground at Bizerte. She was scrapped in Italy in 1921.