In the present study, MoO 3 nanopowder was produced by evaporation of molybdenum oxide powder at high temperature (around 1,000 C) and its subsequent cooling in inert gas. The effect of different parameters such as pressure, temperature, and type of inert gas on the morphology and particle size were examined. The samples were characterized in terms of structure, morphology, particle size, and surface area using complementary techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and the Brunauer-EmmettTeller (BET) method. Particles of the synthesized nanopowder had spherical shape with specific surface area of 18.64 m 2 g À1 and the average diameter of about 31 nm in optimum conditions.