The thermal decomposition of γ-irradiated and unirradiated cobalt(II) malonato complex Na2[Co(C3H2O4)2]·2H2O has been studied by thermogravimetry (isothermal conditions). The reaction order, activation energy and frequency factor were computed by different models. The effect of γ-irradiation on the kinetic parameters of the thermal decomposition reaction is discussed. Radiation did not modify the mechanism of the reaction but accelerated the dehydration step due to the generation of more dislocations in the crystal lattice of the complex. The kinetics of the dehydration is controlled by a phase-boundary (R2 and R3 functions) mechanism, while the decomposition reaction is controlled by a first-order mechanism (F1 function).