Nitrate uptake is an important component of nutrient spiraling in freshwater ecosystems. Anthropogenic activities are increasing nutrient loading in streams and lakes across the globe, which can have profound effects on water quality and community structure. An improved understanding of the mechanisms that govern the processing of nutrients dissolved in streams is necessary to predict and mitigate these effects. Previous research has documented the influence of ecosystem engineering behaviors on physical habitats in both freshwater and terrestrial environments, but the role of ecosystem engineers on nutrient dynamics is less well understood. We investigated how an ecosystem engineer, the net-spinning caddisfly, affects hyporheic exchange and nutrient uptake in 15 replicate stream-analogue mesocosms (SAMs) that were embedded within Cherry Creek in southwest Montana, USA. SAMs were stocked with various caddisfly densities (0 to 5000/m2) and incubated for 22 days to allow the caddisflies to construct their silk nets. Following the incubation period, N-15 labeled nitrate was released into the SAMs and sampled over a 24-hour period to track uptake rates. We found very strong evidence that increasing the density of caddisflies increases the uptake rates of nitrate (p<0.0001). These findings have implications for our understanding of nutrient dynamics in streams where net-spinning caddisflies are present and demonstrate the ability of an ecosystem engineer to substantially alter nutrient cycling in a freshwater environment.