An incubation study was conducted to test the effects of phosphorus (P) addition on nitrous oxide (N2O) emissions from soils taken from two primary forests on lower eastern slope of Mt. Kinabalu, Sabah, Malaysia. Since the ratios of microbial biomass carbon (MBC) to both carbon dioxide (CO2) and N2O emissions reduced significantly by P addition, we suggested that the increase in the efficiency of nitrifying and/or denitrifying respiration by P addition due to the alleviated nutrient deficiency and decreased respiratory need for maintaining microbial activity may have reduced the N2O emissions.