A few monomeric novel oxomolybdenum (V) and cis-dioxomolybdenum (VI) complexes with 2-benzimidazolyl mercaptoaceto hydrazone ligand (LH2) of the general formula [MoO(LH)Cl2] and [MoO2(L).H2O] respectively have been synthesized and characterized by elemental analyses, molar conductance, magnetic susceptibilities, UVVisible, Infrared, 1H NMR and ESR spectral studies. The interpretation of analytical data revealed that the complexes have 1:1 metal to ligand ratio and the ligands exhibit two different types of coordination patterns. The spectral data suggest that, the hydrazone ligands act as monobasic terdentate and exist in keto form in oxomolybdenum (V) complexes whereas in dioxomolybdenum (VI) complexes they act as dibasic terdentate and exist in enol form. ESR spectral data suggest that monomeric nature of oxomolybdenum (V) complexes with distorted octahedral geometry. The thermal stabilities of the complexes have been studied by TG and DTG techniques. The kinetic parameters were calculated from the thermal decompositions of dioxomolybdenum (VI) complexes using Coat’s–Redfern and MKN methods. The antibacterial activity studies have been under taken and results are discussed.