The freshwater fish parasite Leptorhynchoides thecatus contains several cryptic species that vary morphologically, molecularly, and in host use. This study investigated 404 individual fish for the presence of Leptorhynchoides, representing 24 species of fish from Otsego Lake, a glacially formed lake in New York, U.S.A. Of the 24 fish species represented, 12 species were infected with adult Leptorhynchoides in the digestive tract, including 4 species that were infected with gravid female worms: largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieu), rock bass (Ambloplites rupestris), and redbreast sunfish (Lepomis auritus). Individuals from 5 fish species were infected with both adult worms in the digestive tract and with cystacanths in the body cavity. Measurements taken from specimens of the trunks, proboscides, and hooks, along with genetic sequences obtained from specimens at the mitochondrial gene cytochrome oxidase I (Cox1), suggest that the specimens encountered here are the “large form” of L. thecatus. Our survey data provide evidence of the importance of fish as paratenic hosts in the life cycle of L. thecatus and illustrate host use patterns somewhat different than previously reported for members of the L. thecatus species complex. This is the first study, to our knowledge, of a Leptorhynchoides species from the Mid-Atlantic drainage in which morphological, molecular, and ecological data are presented.