This study focuses on the UN's involvement in the peace-building process in CAR. It raises a fundamental problem in international relations, since states are no longer the exclusive actors: the relationship between international organizations and states, or the intervention of a transnational actor in a sovereign state. The CAR is a post-conflict country, the prototype of a fragile and vulnerable state, placed by the international community in the category of "weak states" in need of support. How to understand the UN's involvement in peace-building in CAR is the fundamental question this study sets out to answer. The UN's involvement is seen as an affirmation of its role in maintaining international peace and security, and as a contribution by the international community to the stabilization and perpetuation of peace in CAR, within the framework of multilateral cooperation. The study reveals several political, security and socio-economic obstacles to the peace process in CAR.