γ-Al 2 O 3 supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW 5 O 19 5− , V 2 W 4 O 19 4− , VMo 5 O 19 5− and V 2 Mo 4 O 19 4− ) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and 51V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state 51V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VO x /γ-Al 2 O 3 was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al 2 O 3 surface.