Parasitoids can have significant impacts on the life history of their hosts, as well as on local population and community dynamics. These effects could be particularly pronounced in the Arctic where the breeding season is short. We studied the incidence and loads of egg sac parasitoids, and whether these varied with body size or among species in three Arctic wolf spider species: Pardosa sodalis Holm 1970, Pardosa lapponica (Thorell 1872) and Pardosa moesta Banks 1892 from the Yukon Territory in northwestern Canada. We found a high incidence of egg sac parasitism (by Gelis sp.) and that the incidence of parasitism increased significantly with body size in two of the spider species; however, it did not change in the largest species. Among the three species investigated, parasitism was highest in the largest species (P. sodalis). Parasitism loads ranged from one to fourteen individuals per egg sac, and incidence reached 29.6% overall in P. sodalis. Parasitism may have significant impacts on the life history of tundra wolf spiders.