The Italo-Turkish War with the Ottoman Empire broke out in September 1911 when Italy invaded Libya, and Garioni participated in the war as commanding officer of the 5th Special Division, which included the 11th ‘’Bersaglieri’’ Regiment, 60th Infantry Regiment, 1st Grenadier Battalion, 28th ‘’Bersaglieri’’ Battalion, 6th and 7th Eritrean Battalions, three artillery batteries, and an engineering company, divided into two columns, one under the command of General Clemente Lequio and the other under Colonel General (later General) Alberto Cavaciocchi.

Along with another veteran of the Boxer Rebellion, Luigi Agliardi, Garioni was assigned the task of conquering Zuwarah and Ghadames in western and northwestern Tripolitania on the border with Tunisia.

In June 1913, Garioni was appointed governor of Italian Tripolitania, a position he held until the end of 1914, when he obtained command of the VII Army Corps in Ancona.

After the Allied defeat of Ottoman and German Empire forces in the Battle of Megiddo in Palestine in September 1918 and of Austria-Hungary in the Battle of Vittorio Veneto on the Italian front in late October and early November 1918, Ottoman and German military advisers to the Arab rebel forces in Tripolitania and Cyrenaica abandoned them, leaving them torn by internal strife.

Arab rebel attacks against Italian garrisons in Tripolitania and Cyrenaica declined, allowing Garioni to seize the initiative and put down the rebellion.