This study aims to focus on “Multilevel Constitutionalism,” which derived from the special model of governance in a process of dynamic development of European integration. In the basis of defining the European Union and European community are constitutional sovereignties. This thesis tries to explain Multilevel Constitutionalism’s development and application with the “Treaty in Establishing a Constitution for Europe” and changes in several integration treaties, and explain political constitutionalism developments across two, or more than two levels. Furthermore, this thesis tries to collect the possible influences of Multilevel Constitutionalism in the area of international relation and international law.