Hydroxylammonium nitrate (HAN) monopropellant with its low sensitivity, volatility and toxicity, not only promises a safer substitute to hydrazine but also offers a higher specific impulse and a positive oxygen balance. This study primarily explores the decomposition mechanism and underlying kinetics for a newly developed cerium oxide-based catalyst. The chemical kinetics involved in the thermal and catalytic decomposition was examined through an isoconversional method using thermogravimetric analysis (TG) data. The activation energy (Ea) was evaluated using differential isoconversional method (Friedman's method) and advanced integral isoconversional method (Popescu-Ortega's method). To find frequency factor, compensation effect method (A(CE)) and intercept method (A(0)) were used. Advanced integral method could not provide realistic kinetic parameters while differential method predicted values similar to reported values for thermal decomposition. The values obtained for thermal decomposition were found matching with reported values obtained by other techniques which validated the methodology adopted. The reaction mechanism for both thermal and catalytic decomposition were proposed based on evolved gas analysis. The mechanism proposed was able to describe the variable kinetic parameters extracted from isoconversional method. Overall Ea of thermal decomposition of HAN was similar to 95 kJ/mol. The decomposition over ceria-based catalyst was distributed over three stages namely inception, peak and decay with Ea of similar to 33 kJ/mol, similar to 170 kJ/mol and similar to 130 kJ/mol, respectively. Under identical conditions, iridium-based catalyst show two decomposition stages with Ea of similar to 65 kJ/mol and similar to 120 kJ/mol while final stage being evaporation of HNO3. The ceria catalyst favoured N-2 formation, increased decomposition of HNO3 and enhanced decomposition enthalpy.