Upon being commissioned into the Austro-Hungarian Navy, the three ships of the Monarch class were used for a variety of purposes. All three ships of the Monarch class partook in a cruise around the Adriatic and Aegean in 1899, to display the Austro-Hungarian flag in foreign waters. The Monarch class formed the I Battleship Division of the Austro-Hungarian Navy. The battleship Wien participated in the Diamond Jubilee of the crowning of Queen Victoria in 1897, as well as the international blockade off Crete during the Greco-Turkish War of 1897. However, less than five years after their completion, the Monarch-class battleships were rendered obsolete by the newly commissioned Habsburg class. The newly completed SMS Habsburg conducted a training cruise with the three Monarch-class battleships in January 1903; they were joined by the SMS Árpád the following year. During the 1904 training exercises, the three Habsburg-class battleships engaged the three Monarchs in simulated combat; the maneuver marked the first time two homogeneous squadrons consisting of modern battleships operated in the Austro-Hungarian Navy. The three Habsburg-class ships took over the position of the I Division while the Monarchs formed the newly created II Division. With other new classes of pre-dreadnoughts being built such as the Erzherzog Karl class, and later the Radetzky class, the Monarchs were demoted even further, and ended up in the V Battleship Division. They were serving as coastal defense ships by the beginning of World War I.
World War I
At the outbreak of World War I in July 1914, the three ships of the Monarch class were serving as the V Battleship Division, deployed as coastal defense ships. They also served as training ships, and were used to bombard coastal positions during the early years of the war. In August 1914, the Budapest was transferred from Pula to Cattaro to shell Mount Lovcen. On 9 August 1914 the Monarch shelled the French radio station at Budva. She also bombarded the Montenegrin radio station off Bar on 17 August and another station off Volovica Point on 19 August where she attacked the local radio station and barracks. Following these operations, the Monarch served as a harbor defense ship. On 28–29 December 1915 the Budapest supported the cruisers and destroyers of the Austro-Hungarian Navy that were to raid Durazzo, but the detachment returned to port without having opened fire on the enemy. On 9 January 1916, the Budapest again bombarded the fortifications on Mount Lovcen, and helped to capture the enemy-held mountain. In late 1917 the Budapest and Wien were sent to Trieste, and participated in shelling Italian troops in the Gulf of Trieste. On 10 December 1917, two Italian torpedo boats managed to penetrate the port of Trieste undetected, and fired torpedoes at the battleships Budapest and Wien. The torpedo fired at the Budapest missed, but the Wien was hit twice and sank in less than five minutes in the shallow water of the Trieste harbor. Forty-six men serving on the Wien were killed in the attack. The Budapest was subsequently given the task that the Monarch had been performing for over three years, and was demoted to a floating barrack for German U-boat crews. In June 1918 the Budapest was renovated and had a 380 mm (15 in) L/17 howitzer installed in her bow to use for coastal bombardment, but she never saw action with the new gun in place. At the end of the war in 1918, the remaining Monarch-class battleships, the Budapest and the Monarch, were handed over to Great Britain as war reparations. In 1920 the two ships were sold for scrap to Italy, and were broken up between 1920 and 1922.