The utilization of nitrogen (N) fertilizer in peatlands, with the aim of increasing crop growth and production, is also reported to increase carbon dioxide (CO2) emissions. The application of coal fly ash (CFA) to soil may change soil physico-chemical characteristics, thereby influence carbon mineralization, but its effect on CO2 production is not yet clear. Consequently, the purpose of this study was to quantify the CO2 production of tropical peatlands that received N fertilizer and CFA. In the laboratory experiment, CFA equivalent to the application of 150 Mg ha-1 in the field was added to peatlands with and without N fertilizer. These mixtures were then incubated at 70% water-filled pore space (WFPS) for 30 days at room temperature. Carbon mineralization was measured on a 5-day basis, while several chemical characteristics of treated peatlands, including pH, hot water-soluble C, exchangeable-Ca, -Mg, -Fe, and -Al were measured at the conclusion of the incubation period. This study identified that N fertilizer application increased the CO2 production of tropical peatlands from 29.25 g kg-1 to 37.12 g kg-1. Furthermore, the application of CFA on tropical peatlands reduced CO2 production of tropical peatlands with and without N fertilizer. Decreasing the amount of hot water-soluble carbon from peatlands may account for the reduced CO2 production of peatlands with CFA. The study also showed that exchangeable-Ca, -Mg, -Fe, and -Al increased in peatlands with CFA application, and these multivalent cations were also attributed to a reduction of CO2 production. In conclusion, the negative effects of N fertilizer application on peatlands in increasing CO2 emission may be reduced by the application of CFA.