For most of World War I, Erzherzog Friedrich remained in her home port of Pula, in present-day Croatia, except for four engagements.

Her sole combat engagement occurred in late May 1915, when she participated in the bombardment of the Italian port city of Ancona.

She also attempted to break through the Otranto Barrage in June of that year, but had to retreat when the dreadnought SMS Szent István was sunk.

[2] Her secondary armament consisted of twelve 19 cm (7.5 in)/42 caliber guns, also made by Škoda, mounted in eight single casemates on either wing of the ship and two twin turrets on the centerline.

[3] The ships had a tertiary armament for protection against torpedo boats in the form of the 7 cm (2.8 in)/45 caliber gun, also manufactured by Škoda.

[1] A major mutiny among crews of the armored cruisers stationed in Cattaro, including Sankt Georg and Kaiser Karl VI, began on 1 February 1918.

Following the restoration of order in the naval base, the armored cruisers Sankt Georg and Kaiser Karl VI were decommissioned and Erzherzog Friedrich and her sisters were stationed in Cattaro in their place.

[7] For the morning of 11 June, Admiral Miklós Horthy planned a major assault on the Otranto Barrage; the three Erzherzog Karls and the four Tegetthoff-class battleships were to provide support for the Novara-class cruisers.