This paper considers the complexities involved in the co-management of marine protected areas involving local NGOs. Based on field research in Belize, it examines the interactions between local NGOs involved in the MPA co-management process with state agencies, and local users, focusing on fishers and tour guides. These interactions highlight the fact that the interests of local NGOs and the resource users they represent are not always convergent. Yet the challenges of negotiating the shifting and, at times, divergent interests are ones for which NGOs are often not prepared to meet. This paper argues that, in tandem with training in strategic planning and proposal writing, negotiation and conflict mediation skills are crucial to the success of building positive relations between local NGOs and community stakeholders and, in turn, to fostering long-term success in the co-management process.