Thermal decomposition and the combustion mechanism of ammonium perchlorate/hydroxyl-terminated polybutadiene propellant has been widely investigated during the past decades. The focus in the present work is to investigate the catalytic effect of zinc oxide (ZnO) nano particles on the decomposition mechanism and kinetic behavior of composite solid propellant. Thermal cum kinetic evaluation of the catalyzed and non-catalyzed version of composite propellant has been carried out by four different kinetic methods, including Kissinger method, Flynn-Wall-Ozawa method, Friedman method, and Kissinger-Akahira-Sunose method. Differential scanning calorimetry and thermogravimetry have been used to identify the changes in the thermal and kinetic behavior of the catalyzed composite propellant. The major effect in the catalyzed propellant was lowering of the decomposition temperature by nearly 52 degrees C. The activation energy also decreased, whereas the rate constant increased by the addition of nano zinc oxide confirming the catalytic activity in the composite solid propellant. The activation energy graphs for both versions of the propellant have shown variations with respect to different degrees of conversion.