Helminth parasites of mosquitofish (Gambusia affinis) were surveyed in Bayou Traverse, a waterway in the LaBranche wetlands of southeastern Louisiana, U.S.A. In total, 1,255 parasites belonging to 8 species were collected and identified, including Ascocotyle ampullacea, Ascocotyle mcintoshi, Ascocotyle tenuicollis, Phagicola diminuta, Phagicola sp., Echinochasmus swartzi, Posthodiplostomum minimum, and Glossocercus sp. Adult parasites were obtained by infecting mice (Mus musculus), ducks (Anas platyrhynchos), and chicks (Gallus domesticus) with metacercariae from G. affinis. Bayou Traverse is characterized by snails and fish typical of brackish water habitats and is home to a rich piscivorous bird and mammal fauna. The parasites found in this study are consistent with helminths that parasitize birds and mammals as adults. This study is a survey of the trematodes and cestodes from an estuarine habitat.