New records of hairworms (Gordioidea: Nematomorpha) and mermithid nematodes (Mermithidae: Nematoda) are reported from North American Orthoptera collected over the past 25 y. Several thousand Jerusalem crickets (Stenopelmatidae: Stenopelmatus spp.), field crickets (Gryllidae: Gryllus sp), and several hundred decticine katydids (Tettigoniidae: Tettigoniinae) were captured in the field and maintained alive, serving as potential hosts. A total of 36 specimens were found infected (most multiple), which resulted in the recovery of 19 hairworm lots associated with some 11 species of Stenopelmatus; 6 hairworm lots from 4 species of Gryllus and 2 decticine katydid genera, and 11 mermithid nematode lots associated with 5 species of Stenopelmatus, Capnobotes fuliginosus and a Gryllus sp. The present study identifies hosts of hairworms and mermithids collected from sites throughout central and western United States and much of Mexico.