The thermal decomposition of the thermoelectric CoSb3 alloy was investigated using thermogravimetry (TG). TG curves obtained in inert gas flow with different heating rates were used to perform kinetic analysis based on the Arrhenius equation. Kinetic parameters, such as the effective activation energy, the pre-exponential factor, and the kinetic model function $$ f(\alpha ) $$ , were obtained using the Freeman–Carroll method, the multiheating rates method, and the Coats–Redfern equation. The activation energy was found to be around 200 kJ/mol, and the reaction mechanism for the decomposition of CoSb3 alloy mostly obeys the second-order chemical decomposition process $$ f(\alpha ) = (1 - \alpha )^{2} $$ .