Zinc oxide nanoparticles are fabricated using Ball milling method. For the synthesis of these nanoparticles, 99.9% pure zinc oxide powder is milled for 40 hours. Transmission electron microscopy is employed to study the microstructure of these nanoclusters. It is seen from the transmission electron microscope (TEM) images that the nanoparticles of ZnO are aggregated and form nanoclusters. The diameter of these nanopaticles varies from 5-10 nm, whereas the diameter of these nanoclusters is of the order of several tens of nanometers. The X-ray diffraction technique is used to verify the structure of these synthesized zinc oxide nanoparticles. From the XRD pattern, it is suggested that these nanoparticles are crystalline in nature. The UV visible spectrum shows a broad peak at 380 nm, which is a characteristic of ZnO.