The thermal stability under air of V-doped HfO2 powders was investigated by differential thermal analysis and thermogravimetric analysis (DTA-TG), while the oxidation state of the vanadium inserted in these powders was studied by electron energy loss spectroscopy (EELS). The valence of vanadium for powders prepared under reductive atmosphere was found to be 3+, as well as for powders prepared under neutral atmosphere, whereas powders prepared under air exhibit higher vanadium oxidation states (4+ and/or 5+). The main impurity detected by EELS in V-doped HfO2 powders was carbon. The powders elaborated under air are thermally and structurally stable up to 1000 K. For the V3+-doped powders, the thermal analysis showed the occurrence of irreversible transformations leading to different compounds.