Characterization, thermal stability and thermal decomposition of alkaline earth nicotinates M (C6H5NO2)(2)center dot nH(2)O (M = Mg(II), Ca(II), Sr(II) and Ba(II)), were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), DSC-photovisual system, elemental analysis, complexometry and TG-DSC coupled to FTIR. These compounds were obtained as: mono (Ba), hemi three (Mg), and di (Ca, Sr) hydrated and the TG curve shows that the dehydration occurs in a single step for all the compounds, also for magnesium compound the DTA curve shows to overlap step.In all the compounds the thermal decomposition occurs with the formation of carbonate as intermediate and the respective oxides as final residue, except magnesium one which the thermal decomposition occurs with the formation of magnesium oxide, without formation of carbonate. For the barium compound the TG curve shows that the thermal decomposition of the barium carbonate the mass loss is still being observed up to 1000 degrees C. The results also provided information concerning the thermal stability, thermal behavior and identification of the gaseous products evolved during the thermal decomposition of these compounds. ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)