The synthesis, structural aspects and thermal behaviour of six different magnesium alcoholates are reported. The magnesium oxides obtained by decomposition of the alkoxides show different particle morphologies, as shown by scanning electron microscopy. The mechanism of the thermal decomposition of magnesium methanolate was studied in detail. The substance decomposed in three steps at 90, 330–350 and 360–400 °C. Two intermediates were characterized by elementary analysis (C, H) and IR spectroscopy.