Wetlands are one of the most productive ecosystems in the world. However, they have received little attention in the tropics. Biodiversity data from the Terminos-Centla wetlands is limited despite the conservation efforts to protect these wetlands. In this study we list the medium-szied and large mammals from 8 sites within the Terminos-Centla wetlands. We recorded 30 native and 1 introduced species, representing 9 orders, 14 families, and 27 genera. Four of the recorded species are Threatened, 9 Endangered, and 1 under special protection under Mexican legislation. Compared with other sites of southeastern Mexico, the area of the Terminos-Centla wetlands has a many more species. Our results highlight the Terminos-Centla wetlands as one of the most important systems of Mesoamerica for the medium-sized and large mammals and and underlines the urgent need to develop conservation strategies for the area.