Cobalt-doped titanium dioxide thin films have been successfully deposited using sol-gel spin coating technique. The doping process has been done by mixing cobalt source into TiO 2 sol-gel. The doping concentration has been varied and its effects to the structural, electrical, and optical properties of the thin films have been studied. Reduction in electrical resistivity is observed with the increase of cobalt doping concentration. Higher cobalt doping concentration sample also shows a shift of absorption edge to longer wavelength which is a desired characteristic for application in optoelectronic devices.