This article aims to explain the effort of international governmental organization (IGO) as the third actor in international relations, and this is related to the efforts of solve the problem across the country in the world. This Article discusses the efforts made by the United Nations in resolving diamond conflict Sierra Leone in 1991-2002. This Conflicts is involving rebel groups (RUF) and the government started from dissatisfaction with the bad governance system and becoming larger due to the acquisition of diamond mines to illegal trading of diamonds by RUF. Negotiations by the government to solve the conflict did not go well until there was UN aid to resolve the conflict.