The concept of a global administrative space (GAS) denotes the emergence of administrative structures beyond the territory of the nation state that underpin processes of global governance. Against this backdrop, this chapter argues that an environmental GAS is emerging, which combines the development of independent administrative capacities at the international level with an increasing integration of a broad range of governmental and nongovernmental organizations at different levels of government. The GAS constitutes a complex multilevel and multiactor structure. Based on an original dataset covering issue-specific collaboration and communication flows between organizations operating in the fields of global climate and biodiversity governance, this chapter uses techniques of social network analysis to describe and analyze the structure and composition of administrative networks. It finds a relatively stable pattern of mutual interaction among international environmental bureaucracies, international organizations, national and subnational bureaucracies, research institutes and nongovernmental organizations that can be interpreted as an indicator for the emergence of a GAS in environmental governance.