Overbrowsing has created depauperate plant communities throughout the eastern deciduous forest. We hypothesized these low-diversity plant communities are associated with lower insect diversity. We compared insects inside and outside a 60-year-old fenced deer exclosure where plant species richness is 5x higher inside versus outside. We sampled aboveground and litter insects using sweep nets and pitfall traps and identified specimens to family. Aboveground insect abundance, richness, and diversity were up to 50% higher inside the fenced exclosure versus outside. Conversely, litter insect abundance and diversity were consistently higher outside the exclosure. Community composition of aboveground insects differed throughout the summer (P < 0.05), but litter insects differed only in late summer. Our results demonstrate that the indirect effects of long-term overbrowsing can reduce aboveground insect diversity and abundance, and change composition even when plant communities are in close proximity.