This study examines governance strategies in the Joal Fadiouth Marine Protected Area (MPA) in Senegal with the aim to identify constraints to ensuring biodiversity conservation and socio-economic sustainability for coastal populations. We present a mixed-method empirical analysis that combines participatory mapping, focus group interviews, and individual semi-structured interviews with over 200 individuals from various stakeholder groups. The findings point to two divergent governance realities. One reality is the formal co-management institution – which is tasked with governing a defined space with specific rules, including direct and indirect stakeholder involvement. Another governance reality is that of traditional uses and norms, where, for example, cultural practices contribute to the protection of spawning areas or the conservation of species. Yet another reality is that negotiated in situ by actors who may be from diverse cultural backgrounds operating in an area. At Joal Fadiouth, a key point of misalignment between these realities is that neither traditional authorities nor traditional migrant users of the MPA are represented in the formal decision-making body. This undermines the legitimacy of formal co-management in the eyes of both locals and migrant users. In addition, formal governance has largely failed to consider the vast array of existing cultural and traditional uses of coastal and marine resources, as well as the inclusion of more diverse stakeholders, such as faith-based organizations and women, who are locally important and influential users. As a result, formal zoning and laws do not conform to local expectations, leading to perceptions of illegitimacy that motivate illicit income strategies and a lack of investment into co-management to showcase discontent.