This article outlines the theoretical problematique and some empirical knowledge regarding the impacts of global environmental change on the nation state; thereby it also introduces this special issue of Global Environmental Politics. We argue that global environmental change decreases the capacity of nation states to fulfill their definitional functions without the cooperation of other states. The added stress due to environmental change also increases the demand for adaptive capacities of nation states, which further diminishes their resources to fulfill other core functions. Based on an overview of the complex interplay between global environmental change and the nation state, we focus on the various ways in which the nation state may mitigate, or adapt to, the impacts of global environmental change, including horizontal diffusionism and vertical institutionalism. In summarizing the other contributions to this special issue, we further argue that a reconsideration of key theoretical concepts such as sovereignty, agency, and multilevel governance is required in order to improve our understanding of the complexities of global environmental governance.