Invasions by insect species that become pests are an increasing problem for agriculture. Introductions of parasitoids from the regions of pest origin and breeding plants resistant to invasive pests can reduce invasive pest abundance and impact. Whether interactions between parasitoids and plant resistance are positive or negative depends on the detailed mechanisms. We studied the effects of susceptible versus resistant soybean and avirulent versus virulent soybean aphid on the parasitoids Aphelinus certus and Aphelinus glycinis, the first with a broad host range and the second with a narrow host range. Both parasitoid species parasitized virulent aphids at least as much as avirulent aphids on susceptible and resistant soybeans. Aphelinus certus parasitized fewer avirulent aphids than virulent aphids on resistant soybean and fewer avirulent aphids on resistant versus susceptible soybean. The number of aphids parasitized by A. glycinis did not vary with the treatments. Emergence rates of parasitoid progeny were high for both parasitoids and did not vary with the treatments. Progeny sex ratios of the parasitoids did not vary with plant resistance or aphid virulence. However, for A. certus, there was a small effect of the interaction between plant resistance and aphid virulence. Body masses of female and male progeny of A. certus did not vary with the treatments. However, body masses of female progeny of A. glycinis were larger on susceptible versus resistant soybeans and on virulent versus avirulent aphids. Body masses of male progeny of A. glycinis were larger on susceptible versus resistant plants. Parasitism by A. certus is known to be density-dependent, and given that density-dependent parasitism has been found in several other species of Aphelinus, parasitism by A. glycines is very likely also to be density-dependent. Given the higher densities of virulent versus avirulent aphids on resistant soybean reported in the literature, these parasitoids should parasitize more virulent than avirulent aphids on resistant soybean and would limit the abundance of virulent soybean aphid if much of the soybean acreage had resistant plants. Little research has been published previously on the combined impacts of plant resistance and herbivore virulence on parasitoids. If our results hold true in other systems, plant resistance and biological control may be more compatible in suppressing herbivore virulence than has sometimes been proposed.