The thermal decomposition of nickel nitrate hexahydrate (NiNHH) under dynamic atmosphere of air has been thoroughly studied. Reactions occurring throughout the decomposition up to 600-degrees-C were monitored by means of thermogravimetry (TG) and differential thermal analysis (DTA). These reactions were characterized by analysis of the solid calcination products at different temperatures at which various intermediates were expected. Solid analysis was carried out using infrared spectroscopy and X-ray diffractometry. Non-isothermal kinetic parameters (DELTAE, A and k) were determined. TG and DTA under nitrogen atmosphere has been carried out. The results indicate the formation of Ni(NO3)2.nH2O (where n = 5.5, 4 and 2) and mixture of anhydrous and basic nickel nitrate as intermediate solid products. Basic nickel nitrate intermediate was formed in nitrogen atmosphere as well as in air, which was attributed to a hydrolysis process involving the water of dihydrate intermediate. The morphological changes throughout the decomposition course have been followed by scanning ’electron microscopy and the results are correlated with the obtained thermoanalytical results of the decomposition course of NiNHH.