In the history of Islam, madrasah is the general name of education and training institutions which means buildings or colleges which are produced and taught in course activities. Madrasah constructions are the most modernist and minimalist structures of their age. We can count from the earliest examples of the «Less is More» principle, with spaces that meet the needs program and at the most favorable rates. Mimar Sinan brings the madrasa building tradition to its peak in its location, function, stability and aesthetics. Istanbul is the city where Mimar Sinan's madrasahs are the richest. These buildings that are closed by the law of Tevhid-i Tedrisat in 1924 at Turkey are the groups that have lost their functions. In this study, the architectural characteristics of the Mimar Sinan’s madrasahs of Istanbul, which have gained new functions, have been evaluated.