Our understanding of the controls regulating the rate of litter decomposition is important for improving confidence in the parameterization of carbon cycle–climate feedbacks. Traditional conceptual models rely primarily on climate and lignin/N ratios as the main regulators of decomposition. Here we studied the effects of manganese (Mn) addition on long-term decomposition across 18 substrates in a laboratory incubation. Mn addition remarkably promoted later stage of decomposition, resulting into a smaller fraction of slowly decomposing litter. This dynamic is closely associated with the changes of activities of manganese peroxidase, an important enzyme with greater capacity for lignin degradation. Our findings suggest the necessity of incorporating the interaction of Mn and decomposition into biogeochemical models.