Wildlife in the Great Green Wall (GGW) area, northern Senegal, is threatened by the cumulative effects of anthropogenic activities, drought, and climatic changes. To support conservation planning in line with the GGW management objectives, we studied large mammal diversity in the Koyli Alpha Community Wildlife Reserve in the GGW extension area. We interviewed local communities, made reconnaissance & transect walks, placed camera traps, and carried out fixed point surveys to map the distribution of mammals & to estimate their relative abundance. The surveys were conducted between May 2017 and December 2019. We identified the presence of nine mammal species belonging to six families: one lagomorph, Cape Hare Lepus capensis; seven carnivores, Common Jackal Canis aureus, Pale/Sand Fox Vulpes pallida, Wild Cat Felis silvestris, Marsh Mongoose Atilax paludinosus, Honey Badger Mellivora capensis, Zorilla Ictonyx striatus, Common Genet Genetta genetta, and one primate, Patas Monkey Erythrocebus patas. Our results indicate that the most of the observed species range broadly across the Koyli Alpha Reserve. The Wild Cat and the Sand Fox were also found outside the reserve around the village of Koyli Alpha. Camera trapping events of humans and domestic animals were high throughout the survey area, and the majority of the large mammals observed were mainly nocturnal. The diversity of large wild mammals identified during this study points to the urgent need for the implementation of a management plan of the biodiversity in this area of the Ferlo.