In this paper we explore the challenges involved in engaging the full range of stakeholders needed for effective marine resource management in the transboundary Grenadine Islands shared by the small island developing States (SIDS) of Saint Vincent and the Grenadines and Grenada. The study describes the ways stakeholders were engaged in the development of participatory geographic information systems (PGIS), both in terms of the research approach (process) and the final geodatabase (product); it illustrates how the approach provides a practical means to strengthen aspects of marine governance, particularly in a SIDS context. We found that PGIS can provide a foundation for ecosystem-based transboundary marine governance. The advantages of this approach are two-fold: it provides the fullest possible range of information as input for the management of marine resources and it engages the stakeholders. This engagement takes several forms: capacity to participate in research; ownership of information produced; increased stakeholder understanding; empowerment through access to information; capacity to interact with other stakeholders for information and problem-solving; and competence to participate in actual governance processes. Lastly, we discuss considerations for other practitioners contemplating using PGIS, particularly those working in similar resource-limited SIDS environments.