The lowland tapir (Tapirus terrestris, Linnaeus 1758) is one of the surviving members of the Neotropical megafauna. In Brazil, lowland tapirs are considered vulnerable according to the IUCN Red List of Threatened Species and endangered within the Atlantic Rain Forest biome. We aimed to provide the 1st estimates of density and population size for T. terrestris for Vale Natural Reserve (VNR). We predicted the relationships of 6 covariates to habitat occupancy. Density was estimated by the use of distance-sampling techniques, while occupancy, detectability, and activity patterns were assessed with camera-trap monitoring at 39 sample sites over a 1-year period. Density for T. terrestris was 0.8±0.2 lowland tapirs/km² and population size was 200±33 individuals. Occupancy probability was described by 2 covariates (density of palm trees and distance to water resources) and detectability by those same 2 covariates plus 2 more (distance to road and density of poaching). The species showed the 3 highest peaks of activity at 1900, 2300, and 0400 h. We concluded that VNR still harbors a viable population of lowland tapirs. However, anthropic impacts in the reserve such as poaching and road kills could already be directly affecting the lowland tapir population and producing indirect effects for the whole ecosystem. Results presented herein can be a starting point to support future work in the region and to make predictions regarding the ecosystem relationships, management, and conservation of lowland tapirs.