Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity, and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green tea and Rooibos tea at 530 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect the litter decomposition rates measured after 3 and 12 months. Our study shows that the early to mid-term litter decomposition rates at the global scale were affected predominantly by litter quality (explaining 71% and 52% of the total variance in decomposition after 3 and 12 months, respectively) followed by climate and N deposition. The effect of climate was not litter-specific, and became increasingly significant as decomposition progressed, with MAP explaining 6.2% and MAT 5.9% of the variation. The effect of N deposition was litter-specific, and significant only for 3-month decomposition of Green tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month decomposition rates of Green and Rooibos tea decreased significantly as N deposition increases, explaining 9.4% and 1.0% of the variation, respectively. The expected changes in macroclimate at the global scale by the end of this century are estimated to increase the 12-month decomposition rates of easily decomposable litter by 2.2 – 7.3% and of the more stable substrates by 3.3 – 11.4%, relative to current rates. In contrast, expected changes in atmospheric N deposition will decrease the mid-term decomposition rate of high quality litter by only 3.0 to 4.7% and that of lower quality litter by 1.2 to 1.9% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.