The synthesis, characterization and thermal decomposition studies of Co(II) methanesulfonate are reported. The prepared salt was characterized by Fourier transform infrared (FTIR). The thermal decomposition process was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. It can be verified that Co(II) methanesulfonate contains four molecules of crystallization water, which eliminates in two steps. Under heating Co(II) methanesulfonate suffers three main processes: dehydration, thermal degradation and oxide formation. During thermal degradation, the anhydrous salt decomposes to the mixture Of CoSO4, Co3O4 and Coo in the range of 365-480 degrees C. At about 800 degrees C, the decomposed residue was identified as Co3O4 by X-ray powder diffraction (XRD). The dehydration kinetics of hydrated Co(II) methanesulfonate was studied by TG technology. The activation energies E. of two stages dehydration were estimated by isoconversional methods of Friedman, Ozawa and KAS. (C) 2005 Elsevier B.V. All rights reserved.