Forest conversion into agriculture is a major driver of biodiversity loss in the tropics. In West Africa, Guinea-Bissau lost two thirds of its dense forests over the last two decades due to the unprecedent expansion of cashew orchards. However, the effects of this land-use change on biodiversity remain poorly understood. To address this gap, we examined small mammal species richness, abundance, and composition across 24 sites evenly distributed between forests and cashew orchards in Cantanhez National Park, Guinea-Bissau. Small mammals were live-trapped, molecularly identified, and their diversity related to local (i.e., floor and understorey layers obstruction, canopy openness, palm and liana density, maximum tree height, and tree density and richness) and landscape-scale variables (forest and cashew cover, and edge density). Based on 5,760 trap-nights, we recorded 105 individuals from five rodent and two shrew species. All species were recorded within cashew orchards, while only three were found in forests. Praomys rostratus, the species with the highest number of individuals (n = 72), was found almost exclusively in forests. Species richness increased with understorey obstruction, species abundance decreased with cashew cover, and species composition varied with forest cover, tree height, and canopy openness. Overall, our findings reveal a critical link between both local and landscape-scale variables and small mammal assemblages. Cashew expansion is driving the decline of the forest-dependent P. rostratus, while benefiting generalist and open-area species. We recommend regulating the expansion of cashew orchards to guarantee the persistence of forest-dependent biodiversity in the African tropics.