To assess how elevated N deposition influences leaf litter decomposition dynamics and soil organic matter formation in a temperate deciduous forest, we coupled a reciprocal transplant leaf litter decomposition study with an analysis of the distribution of soil organic matter in mineral associated and particulate organic matter fractions at a long-term, whole-watershed, N fertilization experiment. We found that nearly 30 years of N additions slowed decay rates by about 11% for leaf litter decomposed in the fertilized watershed, regardless of the watershed from which the initial litter was collected. An apparent consequence of the altered rates of decomposition was that the soil in the fertilized watershed had about a 40% greater fraction of SOM in light particulate organic matter compared to the reference watershed, which was positively correlated with the bulk soil carbon to nitrogen ratio. Collectively, our results suggest that under conditions of N saturation, the physical transfer pathway of SOM formation is favored, which can have important implications for the future of the soil organic matter stock and nutrient cycling.