As exotic species invasions continue to transform patterns of biological diversity, it becomes increasingly urgent to understand invasions' full consequences. Woody exotics that colonize closed-canopy forests have the potential for strong effects on plant communities. Berberis thunbergii DC, one such species, has invaded forests throughout eastern North America. Here we quantified the impacts of B. thunbergii invasions on the diversity and composition of native plant communities, both directly and through possible modifications of nutrient, moisture, and light availability. Plots with and without B. thunbergii had similar species richness, evenness, and diversity. Only two species were less likely to occur in plots with B. thunbergii. We also found no effect of B. thunbergii on soil moisture or other key soil properties such as pH and organic matter content. Plots with B. thunbergii had lower light levels at 10 cm from the ground, as under any shrub. It is possible that the invasion we observed may develop into a dense thicket with more severe impacts; however, the effects of B. thunbergii were modest at this time.