Invasive earthworms can affect nitrogen cycling in upland soils, but their importance in riparian zones has not been examined.  Two mesocosm experiments and a field manipulation were used to examine how invasive earthworms affect microbial nitrogen transformation rates and nitrogen flux into adjacent aquatic ecosystems.  In mesocosm experiments, we added earthworms to riparian soil cores, either as mixed species or single species, watered them regularly for 36 days, and collected leachate, which was sampled and added to paired artificial streams.  Leached NH₄⁺-N, NO₃^--N, and TN from the soil cores was positively related to earthworm biomass, and soil cores containing the earthworm Aporrectodea calingosa leached 2X the nitrate of other earthworm treatments.  Through time, P concentration in the streams declined to <2 μg·L^-1 and periphyton became highly P-limited and did not assimilate excess N.  In the field, 0.25 m² riparian plots devoid of earthworms were treated with no earthworms, earthworms added, or artificial burrows.  After 30 days, denitrification rates in plots with added earthworms were 2X those of all other treatments.  Results from these experiments suggest that invasive earthworms (particularily A. calingosa) in riparian zones can cause significant losses of nitrogen both through leaching of nitrate and increased denitrification.