A single-step, nonaqueous, solventless, facile chemical reaction is carried out to synthesize a WSe2 nanoparticles/carbon nanotubes [WSe 2/C] composite at moderate temperature. The use of highly toxic H2Se gas is avoided, reacting elemental selenium powder with W(CO)6 at 750 °C under their autogenic pressure in a closed reactor. Without further processing the as-prepared WSe2/C nanocomposite, detailed characterizations are carried out, and a proposed reaction mechanism is discussed. X-ray diffraction measurements are consistent with the hexagonal phase of WSe2, and the highly crystalline nature of WSe2 nanoparticles is also confirmed by high-resolution transmission electron microscopy pictures. Scanning electron microscopy measurements reveal that WSe2 nanoparticles and carbon nanotubes are formed, with the composition being tracked by C, H, N, S and energy-dispersive X-ray analysis. The Brunauer, Emmett, and Teller surface area analysis technique is implemented for the determination of nitrogen gas adsorption on the surface of the WSe2/C nanocomposite.