Abstract Nanocrystalline 2H–MoSe 2 was prepared from MoO 3, N 2H 4·H 2O, and Se in pyridine at 300°C for 12 h by a solvothermal method. A gray-black product was collected and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The XRD pattern showed that a phase-pure product was prepared. TEM analysis showed that the product was polycrystalline and had plate-shaped particles with a diameter of about 40 nm. The conversion process from MoO 3 to MoSe 2 is discussed.