The global decline of large mammals is widely acknowledged as a major threat to ecosystems worldwide. In West and Central Africa, terrestrial large mammals are particularly threatened by trade and consumption. However, quantitative and scientific information on the population status and conservation of terrestrial large mammals within protected areas in Nigeria is either scarce or extremely limited. This research seeks to help close that information gap. In this study, the abundance, conservation status, seasonal population distribution, and the influence of poaching and vegetation factors on terrestrial large mammals were assessed in Old Oyo National Park, Nigeria, in 2022.