ZnSe nanoparticles have been successfully prepared by hydrothermal method by the reaction of zinc acetate dihydrate with sodium selenite anhydrous in the presence of hydrazine hydrate as a reducing agent. The produced sample was characterized by different techniques such as X-ray powder diffraction (XRD), High resolution transmission electron microscope (HR-TEM), Field emission scanning electron microscope (FE.SEM). The average crystallite size of the as-prepared ZnSe nanoparticles was estimated to be 9.1 nm. The HR-TEM images revealed that zinc selenide nanoparticles have irregular shapes. While the FE-SEM images showed that the produced ZnSe nanoparticles are agglomerated in spherical shapes.