The non-isothermal decomposition of nickel oxalate dihydrate (NiODH) in dynamic atmospheres of air or nitrogen has been investigated by means of TGA, DTA and DSC. The decomposition was followed by examining the decomposition products in each thermal reaction by IR spectroscopy, X-ray diffraction and electron microscopy. The dehydration reaction was endothermic in both atmospheres, giving rise to anhydrous nickel oxalate which still retained some water. On the other hand, the decomposition process was endothermic in air and exothermic in nitrogen. The final decomposition product in air was NiO, whereas in nitrogen the final product was found to be metallic nickel. Morphological changes throughout the decomposition were followed by SEM observations.