A survey of Amistad National Recreation Area in Val Verde Co., Texas, was conducted using field sampling, literature records, and museum vouchers to compile a current list of the mammal fauna. Field work was conducted May 2003–July 2004. Small mammals were trapped along 21 transects for a total of 3,150 trap nights and medium-sized mammals were trapped on nine transects for 135 trap nights. Additional records were obtained through observations, collecting in specific habitats (rocky bluffs, grassy roadsides, etc.), salvaging road kills, and recording visual evidence of presence. Overall, 50 species of terrestrial mammals were identified as probably occurring in Amistad National Recreation Area, including seven non-native species. Previous studies documented 38, 47, and 46 species. With the exception of the northern pygmy mouse (Baiomys taylori), none of the native mammals captured during this study appear to be expanding their range.