At the start of World War I in July 1914, the ship was mobilized into the 2nd Light Squadron and tasked with patrolling the western end of the English Channel. "Guichen" was transferred to the Mediterranean Sea in May 1915, serving initially with the main French fleet that blockaded the Austro-Hungarian Navy in the Adriatic Sea. Later in the year, she was reassigned to the Syrian Division that patrolled the coast of Ottoman Syria, where she helped to evacuate some 4,000 Armenian civilians fleeing the Armenian genocide. By 1917, she had been reduced to a fast transport operating between Italy and Greece. After the war, she took part in the Allied intervention in the Russian Civil War in the Black Sea, but after her crew mutinied in 1919, she was recalled to France, where she was eventually struck from the naval register in 1921 and broken up.