While the scientific community readily collaborates across international borders, the boundaries of administrative units—particularly the nation-state—can be critical in defining the availability of scientific resources, the management of crises and the use of land. Managing border eruptions can be particularly challenging when international relations between the relevant nation-states are strained or complex or when political agendas become involved. Given that over 700 volcanoes lie within 100 km of an international border, and over 1300 are within 250 km, the potential for cross-border eruption impacts is significant. This paper aims to provide an overview of the topic. It presents results from a global study of volcanoes on or near borders and uses five case studies to highlight key issues that arise in the management of risk at such volcanoes. While volcano monitoring provides critical support for hazard assessment and decision-making, its availability depends on the policies of particular governments and institutions. Furthermore, the complexity and diversity of volcanic hazards, activity and impacts can exacerbate existing cross-border inequalities in vulnerabilities, in scientific resources, in disaster management and mitigation capacity and indeed public awareness. We suggest that pre-crisis planning and communication, resource sharing and international agreements can help to mitigate the challenges of cross-border eruptions.