Spatially extensive evidence for nitrogen-induced stimulation of forest growth has been lacking. Analysis of forest inventory data from the northeastern and north-central US collected during the 1980s and 1990s indicates that nitrogen deposition enhanced above-ground carbon storage by 61 kg per kg of nitrogen deposited. Human activities have greatly accelerated emissions of both carbon dioxide and biologically reactive nitrogen to the atmosphere1,2. As nitrogen availability often limits forest productivity3, it has long been expected that anthropogenic nitrogen deposition could stimulate carbon sequestration in forests4. However, spatially extensive evidence for deposition-induced stimulation of forest growth has been lacking, and quantitative estimates from models and plot-level studies are controversial5,6,7,8,9,10. Here, we use forest inventory data to examine the impact of nitrogen deposition on tree growth, survival and carbon storage across the northeastern and north-central USA during the 1980s and 1990s. We show a range of growth and mortality responses to nitrogen deposition among the region’s 24 most common tree species. Nitrogen deposition (which ranged from 3 to 11 kg ha−1 yr−1) enhanced the growth of 11 species and decreased the growth of 3 species. Nitrogen deposition enhanced growth of all tree species with arbuscular mycorrhizal fungi associations. In the absence of disturbances that reduced carbon stocks by more than 50%, above-ground biomass increment increased by 61 kg of carbon per kg of nitrogen deposited, amounting to a 40% enhancement over pre-industrial conditions. Extrapolating to the globe, we estimate that nitrogen deposition could increase tree carbon storage by 0.31 Pg carbon yr−1.