This chapter examines how environmental issues have become increasingly prominent on the international agenda over the last five decades. It considers whether globalization and development must come at the expense of the physical environment, whether state governments can cooperate to protect the planet, and whether climate justice is possible. The chapter first provides a brief history of the development of an international environmental agenda before discussing the functions of international environmental cooperation. It then explores efforts to addres the problem of climate change through the establishment of an international climate regime and highlights the neglect of environmental issues in traditional and realist international relations theory. Two case studies are presented, one dealing with the concept of ‘common but differentiated responsibilities’ and the other with the Alliance of Small Island States (AOSIS) and its influence on international climate politics.