In total, 26 western willets, Tringa semipalmata inornata, were examined for helminth parasites, including 8 spring migrating hosts from the Chihuahua Desert, Rio Grande Valley, Texas, and 18 post-breeding hosts from east central Montana. Sixteen species of helminth parasites were present in component communities for both spring migrants and post-breeding birds. There were 9 species of trematodes, 2 cestodes, and 5 of nematodes, with a total of 1,593 individual specimens (X  =  99.6, ±SE  =  57.9, M  =  9) present in migrating willets, and 5 species of trematodes, 8 cestodes, and 3 nematodes for a total of 1,148 individual specimens (X  =  71.8, ±SE  =  34.4, M  =  12) present in post-breeding hosts. Species richness in infracommunities ranged from 2 to 10 (X  =  5.1, ±SE  =  0.95, M  =  5.3) for spring migrants, and from 1 to 4 (X  =  2.8, ±SE  =  0.26, M  =  3) for post-breeding birds. Diversity and evenness were 0.72 and 0.23 for spring migrants and. 0.62 and 0.17 for post-breeding hosts. Trematodes were the dominant taxa in spring migrants and cestode taxa in post-breeding hosts. Helminths with marine-associated life cycles were present in larger numbers in spring migrants from the Rio Grande Valley (11 of 16 species) than in post-breeding hosts from Montana hosts (4 of 16 species). The higher number of marine species in spring migrants was probably related to their more recent association with a marine habitat. Several species of Anomotaenia were major contributors to the component communities in both localities. Four species of nematodes with large prevalence, i.e., Schistorophus skrjabini, Sciadiocara umbellifera, Skrjabinoclava inornatae, and Sobolivicephalus lichtensfelsi, observed in spring migrants from the Rio Grande Valley were absent from Montana hosts. There was only a 2% similarity between the Rio Grande Valley and Montana. All helminth species, except for the possibility of Anomotaenia spp., were generalists. A checklist of helminth parasites of the willet is included.