The new compounds Pyridoxal N-allyl-S-methylthiosemicarbazone (L) and the dioxomolybdenum(VI) complex [MoO2(L)CH3OH] have been synthesized and characterized by elemental analysis, UV–Vis, FT-IR, Raman and 1H NMR spectra, and also by the single crystal X-ray diffraction technique. Single crys- tals of the cis-dioxomolybdenum(VI) complex were obtained by evaporating its methanol solution. According to the single-crystal X-ray diffraction investigation, the molybdenum atom in the complex is in a distorted octahedral coordination. The sixth coordination site is occupied by the oxygen atom of a methanol solvent molecule. The methanol coordination between the oxygen and molybdenum atoms is the weakest bond, with a MoAO bond length of 2.355 Å. The geometries and vibrational spectra of the pyridoxal thiosemicarbazone (L) and its complex are explained by quantum chemical calculations.