Histomoniasis is a significant disease of gallinaceous birds caused by Histomonas meleagridis. Transmission of this parasite is dependent on use of the cecal nematode Heterakis gallinarum. To define the host range of this nematode, cecal contents from 399 game birds and poultry, representing eight species, were examined for Heterakis spp. The majority of these species (five of eight) were infected with Heterakis nematodes. Heterakis gallinarum was detected in free-ranging wild turkeys (Meleagridis gallopovo), captive-raised ring-necked pheasants (Phasianus colchicus), chukars (Alectoris chukar), and domestic chickens (Gallus gallus domesticus), whereas H. isolonche was found in ruffed grouse (Bonasa umbellus). No Heterakis species were identified in the domestic turkey (Meleagridis gallopovo), American woodcock (Scolopax minor), and dabbling duck (Anas spp.) samples. Genetic characterization indicated that nematodes identified as H. gallinarum were present in two distinct clades. One clade of H. gallinarum sequenced from this study grouped with chicken-derived sequences from other countries. The other group of sequences consisted of a sister clade to a group of parasites morphologically identified as H. isolonche. Currently it is unknown if this group represents a genetic variant of H. gallinarum, a variant of H. isolonche, or a novel species. These results indicate Heterakis infection varies among poultry and game bird species but is common among select gallinaceous species in Pennsylvania.