A complete dentition of Edaphodon hesperis, sp. nov., is described from the Upper Cretaceous (lower Campanian) Haslam Formation of Vancouver Island, British Columbia, Canada. It is one of the complete specimens for Edaphodon, most species of which are known only from incomplete toothplates. This is the first Cretaceous Edaphodon from western North America, extending the geographical range of the genus from its original distribution in Australia, Europe, New Zealand, and eastern North America. The specimen also extends the stratigraphic range of the genus in North America to the lower Campanian. Edaphodon hesperis, sp. nov., is characterized by a deep symphyseal surface and a distally located posterior outer tritor with reduced size on the mandibular toothplate. The vomerine toothplate has six tritorial pads on the oral surface. A phylogenetic analysis based on discrete characters of the mandibular toothplate indicates that the new species is basal among the eight species of this genus for which a nearly complete mandibular toothplate is known. A linear discriminant analysis shows that the new species is morphologically distinct from four other Edaphodon species based on continuous characters on the mandibular toothplates.