During the education reform process of the Ottoman Empire, Thessaloniki always had a significant place. In Thessaloniki, a variety of schools were established by foreigners at the levels of primary and secondary education and high school. These schools were established by France, Italy, England, Germany, the USA and Romania. This study aims to provide an insight into the foreign schools established in Thessaloniki during the period of Ottoman education modernization. To this end, these schools established in the name of different countries were examined in terms of their educational activities, their missions, the efforts of the Ottoman administration to control them, and also the problems experienced.