Abstract: WSe₂ nanoparticles with an average diameter of 30 nm and Club-shaped WSe₂ nanostructures of 6 nm diameter were prepared using solid state reaction with the tungsten and selenium powders in Ar atmosphere after high energy ball milling or direct gland. The morphology and microstructure were characterized by using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The tribological properties of HVI500 base oil with and without WSe₂ nanostructures as additive are investigated on a UMT-2 multispecimen tribotester. Friction coefficient of the base oil containing 5% WSe₂ nanostructures is lower than that of the base oil and decreases with increasing load. WSe₂ nanostructures are good lubricating additives for HVI500 base oil.