Fifty-six speckled rattlesnakes, Crotalus mitchellii, from western North America were examined for helminths. One species of Cestoda (tetrathyridia of Mesocestoides sp.) and 5 species of Nematoda (gravid adults of Abbreviata terrapenis, Physaloptera abjecta, Thubunaea cnemidophorus, and Travassoascaris araujoi and larvae of Physocephalus sp.) were found. Travassoascaris araujoi had the highest prevalence and greatest mean intensity of helminths infecting C. mitchellii. Three new host records for C. mitchellii are reported. As has been reported for other North American rattlesnakes, C. mitchellii is parasitized by “generalist” helminths.