The countries of the Wider Caribbean Region (WCR) are linked economically by their transboundary living marine resources. The region is facing a continued decline of these resources. Science is improving our understanding of the human contributions to this decline, but national policies and programmes have not kept pace with this understanding. The Caribbean Regional Seas Programme and its Cartagena Convention and Protocols provide the regional legal framework for protection and sustainable management of the WCR's living marine and coastal resources. This article focuses on the Cartagena Convention's Protocol for biodiversity conservation, the Protocol Concerning Specially Protected Areas and Wildlife (SPAW), arguing that governments and organizations need to significantly increase participation in this regional treaty regime to effectively address transboundary environmental challenges. A new initiative, the Global Environment Facility-supported Caribbean Large Marine Ecosystem project, will help in this effort. International policy supports strengthened regional seas programmes. It is now imperative for all levels and sectors to assist governments in strengthening this important treaty regime for biodiversity conservation in the Wider Caribbean Region.