ZnO nanoparticles were synthesized by co-precipitation method. The synthesized particles were characterized by Xray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray spectroscopy (EDX) and UV-visible spectroscopy. The X-ray diffraction study reveals that the synthesized ZnO nanoparticles have wurtzite structure and the particle size varies from 35 to 40 nm. HRTEM investigation reveals that the surface morphology of ZnO nanoparticle is spherical in co-precipitation. The UV-Visible spectrum of the nanoparticles shows a red shift compared to that of the bulk sample.