In order to promote a more sustainable management of marine biodiversity, ecosystems and fisheries, numerous experts recommend implementing an Ecosystem-Based Fisheries Management (EBFM). The idea underlying EBFM is to consider various complexities, including trophic, habitat and socio-economic interactions. Illegal, unreported and unregulated (IUU) fishing is a significant element of these complexities, especially for small-scale fisheries. We advance the EBFM on the coastal fishery of French Guiana, considering the high impact of IUU fishing in this case study. We rely on a multi-species resource-based dynamics and a multi-fleet model integrating IUU fishing. From the calibrated model, two contrasted projections, including IUU fishing or not, highlight the impact of illegal fishing on the ecosystem and fishery dynamics. Our results stress the considerable potential bioeconomic gains in biomass, catch and landed value associated with reducing illegal fishing. Policy recommendations are deduced from these findings.