Prior to World War I, the territory of the county belonged to Austria-Hungary and mostly was contained in the Szatmár County of the Kingdom of Hungary. In the aftermath of the war and the ensuing Hungarian–Romanian War, the Romanian Army entered the county in early 1919, and its administration passed to the Kingdom of Romania. The territory of Satu Mare County was transferred to Romania from Hungary as successor state to Austria-Hungary in June 1920 under the Treaty of Trianon.