Chelonibia testudinaria (Sea Turtle Barnacle) and other closely related barnacle species of the genus Chelonibia are known to utilize a variety of organisms for their attachment substrate. These include the calcified exoskeleton of marine crustaceans and chelicerids, the epidermis of manatees, and the carapace regions of all extant sea turtle species. Here, we present the first records of an Alligator mississippiensis (American Alligator; Alligatoridae) as a host for C. testudinaria.