Cobalt doped zinc oxide nanoparticles were prepared through simple chemical precipitation method. X-ray diffraction studies confirm the prepared particles are in Wurtzite structure. Scanning Electron Microscopy and TEM studies show the shape and morphology of the particles. To identify the presence of cobalt in ZnO, XRD and FTIR studies were done. A thermal property of undoped and doped ZnO were studied by TGA &DTA analysis. Optical absorption measurements confirm the presence of exciton peak at 341 nm. Photoluminescence studies were done with the excitation wavelength of 395 nm.