Abstract: The first decade of the new millennium brought a series of already historical facts, which the international society is called to deal with, understand and solve based on the assumption that the solutions are only possible if thought of and implemented in an integrated, solidary and multilateral way. This need of cooperation also makes the world more interdependent than before, confirming a new logic of power in international relations. General environmental problems, as well as those related to human rights, finances, trade, among others, may only have satisfactory solutions if negotiated and regulated by all the states, without disregarding the role played by new agents in the international scenario. The emerging global environmental issues, particularly climate change, have been challenging the international system to adopt effective measures to face this problem on an urgent basis, at the risk of aggravating the resulting social, economic, political and environmental impacts. The Environmental International Law has been facing these issues in an innovating way, incorporating a new form of global environmental governance based on which new players are brought to the discussion and implementation of measures to face environmental problems. Among these players, we should highlight the subnational regional governments and their horizontal networks of actions and insertions in the decision making scenario. The purpose of this article is to explore the role of subnational governments and their networks in the development of global climate governance and in the consolidation of the international environmental law, particularly the Network of Regional Governments for Sustainable Development (nrg4SD).