Background and Aims Atmospheric nitrogen (N deposition has elevated rapidly in tropical regions where N₂-fixing tree species are widespread. However, the effect of N deposition on litter decomposition in forests with N₂ -fixing tree species remains unclear. We examined the effect of N addition on litter decomposition and nutrient release in two tropical plantations with Acacia auriculiformis (AA, N₂-fixing and Eucalyptus urophylla (EU, non-N₂-fixing in South China. Methods Three levels of N additions were conducted: control, medium-N (50 kg N ha⁻¹ yr.⁻¹ and high-N (100 kg N ha⁻¹ yr.⁻¹ in each plantation. Results Initial decomposition rate (ka for the control plots was faster in the AA plantation than in the EU plantation, but later in decomposition, larger fraction of slowly decomposing litter (A remained in the former. N addition increased the slow fraction (A, decreasing soil microbial biomass and reducing acid-unhydrolyzable residue (AUR degradation in the AA plantation. In the EU plantation, however, N additions significantly increased initial decomposition rate (ka and soil N availability. Furthermore, N addition decreased litter carbon and N release (in the AA plantation, while litter phosphorus release also decreased in both plantations. Conclusions With ongoing N deposition in future, tropical plantations with N₂-fixing tree species would potentially increase carbon accumulation and nutrient retention in forest floor by slowing litter decomposition.