Complex environmental issues have to date mostly been addressed by administrative means such as regulation, impact assessment, and planning that harness expertise in institutions such as pollution control agencies and resource management bureaucracies. Administrative rationalism is defined as the problem-solving discourse that emphasizes the role of the expert rather than the citizen or producer/consumer in social problem solving. Experts can be scientists, social scientists, or policy analysts who can deploy techniques such as cost-benefit analysis and risk analysis. Recent variations on the discourse involve evidence-based policy making and ‘nudge’. Administrative rationalism figures more strongly as an institutional style in some political systems than in others. The chapter focuses on the United States, as it pioneered many of the practices of administrative rationalism in environmental policy, and China, where administrative rationalism now finds its strongest application. Administrative rationalism is in crisis as its limits when confronting complexity become exposed, and it is arguably giving way to more networked and less hierarchical governance.