The paper suggests that a closer focus on the impact of institutions for governance offers opportunities for a fruitful integration of the main approaches to European integration. The paper looks first into the common roots of neo-functionalism and regime theory and locates them in the middle ground between realism and legalism. Subsequently, it develops a concept of institutionalised international governance that introduces an institutional perspective into the dominant approach to international regimes and applies it to the European Community. Finally, it opens the static concept for feedback effects and development over time. Concludes that the analysis of institutionalised international governance within the horizontally structured international system may in fact develop an international relations perspective that focuses on horizontal coordination among states without simply disregarding the institutional particularities of the Community.