Early successional ruderal plants in North America include numerous native and nonnative species, and both are abundant in disturbed areas. The increasing presence of nonnative plants may negatively impact a critical component of food web function if these species support fewer or a less diverse arthropod fauna than the native plant species that they displace. We compared arthropod communities on six species of common early successional native plants and six species of nonnative plants, planted in replicated native and nonnative plots in a farm field. Samples were taken twice each year for 2 yr. In most arthropod samples, total biomass and abundance were substantially higher on the native plants than on the nonnative plants. Native plants produced as much as five times more total arthropod biomass and up to seven times more species per 100 g of dry leaf biomass than nonnative plants. Both herbivores and natural enemies (predators and parasitoids) predominated on native plants when analyzed separately. In addition, species richness was about three times greater on native than on nonnative plants, with 83 species of insects collected exclusively from native plants, and only eight species present only on nonnatives. These results support a growing body of evidence suggesting that nonnative plants support fewer arthropods than native plants, and therefore contribute to reduced food resources for higher trophic levels.