Historically, the central actor in the story of international law has been the nation-state, which has led to a rich array of theories about state behavior, such as realism, liberalism, and constructivism that continue to dominate the study of international law and relations. Today, new challenges such as terrorism, climate change, non-international armed conflict, and cyberespionage require new approaches that ask international law to motivate and constrain the behavior of individuals in addition to nation-states. This has put the study of human behavior at the center of international legal scholarship prompting the rise of behavioral approaches in international legal scholarship. Neuroscience has been critically missing from this discourse even as it is leading the way in providing evidence-based research about human cognition and brain-behavior connections. This chapter introduces neuroscience to the study of international law. It provides a general foundation for understanding the field of neuroscience, describes the existing literature at the intersection of law and neuroscience – neurolaw – and considers how to begin constructing the foundations, frameworks, and central agenda for interdisciplinary connections between neuroscience and international law. The chapter concludes by identifying several areas of study in international law that may benefit from neuroscientific insights.