This study compares the helminth faunas between Cope's gray treefrogs ( Hyla chrysoscelis ) and green treefrogs ( Hyla cinerea ), in areas where they have recently overlapped due to range expansion by H. cinerea , to determine whether or not 2 species of frogs with a high degree of similarity in many of their life history traits also exhibit similarities in the composition of their helminth assemblages. Results of this study did not find significant differences in helminth species diversity when sympatric and allopatric populations of the same species of frog were compared. There was, however, a significant difference in helminth diversity among sympatric populations of H. chrysoscelis and H. cinerea , and this difference was in large part attributable to the significantly higher abundance of the gastrointestinal nematode Cosmocercoides variabilis among H. chrysoscelis . Additional studies will be required to determine whether the observed patterns are due to differences in arrival time, perch locations within the chorus, or parasite-mediated competition.