Differential thermal analysis (DTA) was used to examine the effect of the particle size and morphology of Co₃O₄ on its thermal response under exposure to 1 % CH₄. The DTA response results from the catalytic oxidation of methane. Co₃O₄ samples differing in particle size and morphology were produced by ball milling or were synthesized. The investigations performed with temperatures between 250 and 450 °C reveal that both particle size and shape have a considerable effect on thermal response.