In this first note, the Trichostrongyloidea belonging to the Nematodirinae parasites of Ruminants from Alberta are identified. New morphological data were given on Nematodirella antilocaprae (Price, 1927) parasite of Antilocapra americana. Nematodirus andersoni n. sp. is described from Ovis canadensis. Because of the deep indentation of the dorsal lobe, the species is similar to N. bioccai Rossi, 1983 parasite of Ovis aries in Iran. However, it is different in the reduced number of cuticular ridges of the males and by the small indentation between the dorsal lobe and the lateral lobes. In our opinion, the species of nematodirus identified as N. archari from Ovis canadensis in North America, are probably N. andersoni.