1. Although it is widely believed that non-native invasive species threaten the functional integrity of forest ecosystems, their impact on important ecosystem processes such as nitrogen (N) cycling is not well understood. 2. To examine how invasive species alter ecosystem N dynamics, we established monocultures of five phylogenetic pairs of native and non-native invasive understory woody species common to Eastern U.S. forests. 3. After three years, we found invaders increased N cycling by enhancing the flow of N to the soil through greater litter N production and litter N content, and increased the uptake of available soil N, via greater fine root production and specific root length. 4. Synthesis – Our results highlight the importance of linking above- and below-ground processes to better understand invader impacts on ecosystem nutrient processes. The rapid shifts in soil N processes as a result of invader dominance observed in our study suggest that invaders may be an important driver of forest ecosystem functioning.