Globally, historical environmental shifts have been shown to have had strong impacts on genetic diversity in many species, in some cases causing population bottlenecks or fragmentation. Over the millennia, Central Africa has been characterized by tumultuous environmental changes. Extreme rainforest contractions occurred during the last glacial maximum about 12,000 years before present (YBP), and during the “rainforest crisis” of 2500 YBP, which has been attributed to either climate change or anthropogenic influence. Genetic evidence from contemporary populations suggests that the resulting forest fragmentation had an important role in the evolution of modern forest-dwelling species in the region, instigating diversification and population structure. Past researchers have speculated that the apparent divergence of the northern and southern populations of mandrills (Mandrillus sphinx), a primate endemic to central Africa, may have been partially due to Pleistocene-era contraction of rainforests into northern and southern refugia. However, the effects of the region’s changing climate on mandrill effective population size have thus far been unknown. We used microsatellite data collected from a wild mandrill population in Gabon to explore the demographic history of this species as it correlates with past environmental changes. We found no evidence that these shifts were associated with population bottlenecks in this species, suggesting that their populations historically were numerous and capable of weathering major environmental changes.