For primates, as for most other animals, the abundance and distribution of food resources and the risk of predation are generally considered primary determinants of their social organization. The overall objective of this project is to characterize the availability and diet of the Guinea baboon in the Niokolo Koba National Park, particularly in the Simenti sector. Descriptive information on plant phenology was needed to determine seasonal changes in food availability. Thus, the results show that there are more tree species available as the season becomes drier, the month of April with more plants available 15 species, the month of March with 12 species and the month of February 10 species. So, to find out which species the baboons consumed during our study, we followed the baboons for 47 days to collect data on their diet and daily activities from 6: 30 a.m. to 1 p.m. Thus, we were able to monitor several different groups, of which several parameters (daily activities) were listed. The results reveal for the three months of collection to give out of 986 events observed, the 526 concern the food, either 54.34% more than half of the events. Thus, the Guinea baboon spent most of its time satisfying its nutritional needs than focusing on its other activities such as socialization (81 events), movements (128 events), rest (251 events). The analysis show also that Guinea baboons are eclectic omnivores, they consume much more plants than other types of food. Plants account for 89.67% of their general diet, insects 7.46%, mammals 0.24%, and other foods 1.86%. Considered omnivorous with a frugivorous tendency, baboons show a preference for fruits on all parts of plants consumed with a proportion of 79.36%, for roots 6.2%, flowers 5.8%, bark and fiber 3.83% and for leaves sap and stems the least consumed parts with 4.80%). However, not all species were consumed at the same rate. The best consumed species were: Piliostigma thonningii, Strychnos spinosa, Cyperus rotontus and Mimosa pigra.