Non-isothermal decompositions (including TG, DTG, DTA and DSC) of nickel malonate dihydrate and of nickel hydrogen malonate dihydrate were studied in different dynamic atmospheres of N-2, H-2 or air. The reaction of the hydrogen malonate salt commences at a lower temperature than the corresponding nickel malonate salt. IR spectroscopy showed that nickel acetate was formed as a reaction intermediate during the decompositions of both reactants. X-ray diffraction showed that nickel metal was the predominant product from reactions in N-2 or H-2 atmospheres while nickel oxide, together with some nickel metal, was formed during reaction in air. Gas chromatography identified CO2, CO, acetic acid ethyl alcohol together with appreciable amounts of methyl formate and ethyl formate as the volatile decomposition products. Kinetic and thermodynamic parameters of the decomposition of the two reactant salts were calculated.