Although macroinvertebrate communities play a key role in the cycling of nitrogen (N) and phosphorus (P) in streams, this process may be disrupted through decreased macroinvertebrate diversity or abundance from agricultural inputs of nutrients, sediments and pesticides. However, it is unclear how such community changes affect their biological storage of N and P. In 2010 and 2011, we collected water samples and macroinvertebrates from 14 streams in New Brunswick, Canada, with catchments representing a gradient in agricultural cover (0–92%, mainly potatoes). Macroinvertebrate communities were dominated by aquatic insects, and individual families were weighed for biomass and analyzed for N and P content as well as δ15N, an indicator of excess nutrients. Aqueous total P and total N increased significantly with agricultural cover, whereas macroinvertebrate community biomass and richness decreased. Within 6 of 9 taxa, δ15N values increased with agricultural cover. N content varied among families, with the lowest (average ⁓8.5%) values in Baetidae, Ephemerellidae, Chironomidae and Simuliidae, and the highest (average ⁓10.1%) values in Perlidae, Chloroperlidae and Elmidae adults. In addition, P content was significantly higher in Chironomidae (0.63%) than Perlidae (0.42%), Chloroperlidae (0.32%), and Hydropsychidae (0.42%). However, no individual families showed a significant change in their N or P content across sites. Community nutrient storage (CNS g/m2; sum of family nutrient content %N or %P * family biomass g/m2) for both N and P was not related to agriculture in the catchments whereas community nutrient content (CNC; the average %N or %P of all families weighted by their relative biomass) increased for P and decreased for N with higher agriculture. Overall, these results suggest that agricultural inputs of nutrients and other materials affect storage of N and P in stream macroinvertebrate communities, likely through impacts on community biomass and diversity.