At the outbreak of World War I in at the end of the month, Greece's pro-German monarch, Constantine I, decided to remain neutral.
The Entente powers landed troops in Salonika in 1915, which was a source of tension between France and Greece.
Ultimately, the French seized the Greek Navy on 19 October 1916 (see Noemvriana and National Schism).
Lemnos was reduced to a skeleton crew and had the breech blocks for her guns removed to render them inoperable.
All ammunition and torpedoes were also removed.
Ultimately, a pro-Entente government under Prime Minister Eleftherios Venizelos replaced Constantine and declared war on the Central Powers.
Lemnos, however, did not see active service with Greece's new allies, and instead was used solely for harbor defense until the end of the war.

After the end of World War I, Lemnos joined the Allied intervention in the Russian Civil War and served with the Crimean Expedition.
There, she aided the White Russians against the Communists.
In April 1919, Lemnos was present in Kaffa Bay, where she provided gunfire support to the Volunteer Army.
On 22 April, aerial reconnaissance reported that the Red Army was massing in the town of Vladislovovka; Lemnos and the British light cruiser HMS Caradoc bombarded the town, forcing the Soviet forces to withdraw.
She then saw service during the Greco-Turkish War, where she supported landings to seize Ottoman territory.
The Ottoman Navy had been interned by the Allies after the end of World War I, and so provided no opposition to the Greek Navy's activities.

In February 1921, Lemnos was stationed in Smyrna to support the occupation of the city.
Operations came to a close in September 1922 when the Greek Army was forced to evacuate Smyrna by sea, along with a sizable number of civilians from Asia Minor.
The fleet transported a total of 250,000 soldiers and civilians during the evacuation.
Lemnos departed Smyrna on the evening of 8 September with her sister Kilkis.
While en route from Smyrna to mainland Greece, Captain Dimitrios Fokas, the commander of Lemnos, formed a Revolutionary Committee with Nikolaos Plastiras and Stylianos Gonatas, two colonels who supported Venizelos, who had been ousted in 1920.
The men launched the 11 September 1922 Revolution, and other vessels in the fleet mutinied in support of the coup.
King Constantine I was forced to abdicate in favor of his son, George II.

In 1932, Lemnos was placed in inactive reserve; sections of her armor plate was removed to build fortifications on the island of Aegina.
She was disarmed in 1937 and thereafter used as a barracks ship.
At the outbreak of World War I in at the end of the month, Greece's pro-German monarch, Constantine I, decided to remain neutral. The Entente powers landed troops in Salonika in 1915, which was a source of tension between France and Greece. Ultimately, the French seized the Greek Navy on 19 October 1916 (see Noemvriana and National Schism). Lemnos was reduced to a skeleton crew and had the breech blocks for her guns removed to render them inoperable. All ammunition and torpedoes were also removed. Ultimately, a pro-Entente government under Prime Minister Eleftherios Venizelos replaced Constantine and declared war on the Central Powers. Lemnos, however, did not see active service with Greece's new allies, and instead was used solely for harbor defense until the end of the war.
After the end of World War I, Lemnos joined the Allied intervention in the Russian Civil War and served with the Crimean Expedition. There, she aided the White Russians against the Communists. In April 1919, Lemnos was present in Kaffa Bay, where she provided gunfire support to the Volunteer Army. On 22 April, aerial reconnaissance reported that the Red Army was massing in the town of Vladislovovka; Lemnos and the British light cruiser HMS Caradoc bombarded the town, forcing the Soviet forces to withdraw. She then saw service during the Greco-Turkish War, where she supported landings to seize Ottoman territory. The Ottoman Navy had been interned by the Allies after the end of World War I, and so provided no opposition to the Greek Navy's activities.
In February 1921, Lemnos was stationed in Smyrna to support the occupation of the city. Operations came to a close in September 1922 when the Greek Army was forced to evacuate Smyrna by sea, along with a sizable number of civilians from Asia Minor. The fleet transported a total of 250,000 soldiers and civilians during the evacuation. Lemnos departed Smyrna on the evening of 8 September with her sister Kilkis. While en route from Smyrna to mainland Greece, Captain Dimitrios Fokas, the commander of Lemnos, formed a Revolutionary Committee with Nikolaos Plastiras and Stylianos Gonatas, two colonels who supported Venizelos, who had been ousted in 1920. The men launched the 11 September 1922 Revolution, and other vessels in the fleet mutinied in support of the coup. King Constantine I was forced to abdicate in favor of his son, George II.
In 1932, Lemnos was placed in inactive reserve; sections of her armor plate was removed to build fortifications on the island of Aegina. She was disarmed in 1937 and thereafter used as a barracks ship.
Greek battleship Lemnos