In the thinking of neoliberal institutionalism, international organizations are capable of increased collaboration between national governments in global issues and to act independently of the wishes of superpowers on the international scene. This research has attempted to test the gains made under the neoliberal doctrine, associated with the role played by international environmental organizations in the challenges of economic relations of North-South, through the "analysis of competing hypotheses" method. For this purpose, two other hypotheses were developed to compete with the main hypothesis showing the interests of both North and South countries with regard to international organizations. Among the various efforts of the United Nations as the largest international organization active in the environmental arena, five important diplomatic meetings – namely, Stockholm, Rio, Kyoto, Johannesburg and Copenhagen – were selected and judged on the basis of each of the competing hypotheses. The findings of this study show that international organizations have been continuing the policy of capitalist countries in the economic relations between North and South, rather than promoting environmental concerns. The interests of countries of the South have been the lowest of their priorities.