Baboons occur in a large range of different habitats. However, data on the ecology of Guinea baboons were scarce. We provide information on the ranging behaviour, habitat use, and diet of a population of Guinea baboons in the Niokolo-Koba National Park, Senegal. Home ranges were about 25 km², and they moved up to 13 km per day. They seem to prefer the more forested parts of their home range near the river. Fruit dominates their diet, and the nuts of the palmyra palm are a year-round food source.