Thermogravimetric analysis was used to study the thermal behavior of Acacia mangium wood under inert atmosphere at heating rates ranging from 5 to 15C min -1, from room temperature to 800C. Weight losses of A. mangium wood in inert atmosphere were found to occur in three stages. These three states are generally associated with the decomposition of the three main components of the lignocellulosic materials. Most decomposition occurred in the range of 300-400C (80% weight approximately). The kinetic parameters of the process were evaluated using the independent parallel reaction model, attributed to the three main components of lignocellulosic materials: hemicelluloses, cellulose, and lignin. The values of activation energy, preexponential factor, and contribution factor were similar to those reported in other studies for this type of biomass. The model proposed predicted an acceptable correlation between the experimental and the calculated curve to the decomposition of A. mangium, with an error of less than 3% of deviation in the temperature range studied