Freshwater rivers and streams are threatened by anthropogenic additions of bioavailable nitrogen from fertilizers and urban waste. Exposure to excess nitrate influences the survival, growth, and recruitment of freshwater species and has been shown to increase susceptibility of these species to other stressors such as high temperatures and low oxygen. To address the threat of nitrate pollution in freshwater ecosystems, it is necessary to better understand the mechanisms underlying nitrate removal, including biotic nitrogen uptake and denitrification. Net-spinning caddisflies (Hydropsychidae) are widespread and locally abundant freshwater ecosystem engineers that spin silk nets and retreats. These silk structures have been documented to affect streambed hydrology and enrich associated microbes in denitrifying genes compared to nearby rock biofilm controls. Using SUNA V2 Nitrate Sensors (Sea-Bird Scientific) in a laboratory-based mesocosm study, we collected high frequency nitrate concentrations over 24-hours to determine the rate of nitrate removal in treatments containing caddisfly silk structures, biofilm from rock surfaces, and filtered stream water controls. While stream water controls exhibited constant nitrate concentrations, the caddisfly silk structure and rock biofilm treatments both exhibited linear decreases in nitrate levels. Our findings indicate that caddisfly silk structures are likely an overlooked source of nitrate removal in freshwater rivers and streams, possibly comparable to streambed biofilms, which extensive research has demonstrated regulate whole-stream nitrogen cycling.