Chemical bath deposition method was used for preparation of Cd1-xCoxS thin films. The effects of Co doping and thermal annealing on structural, optical, electrical and magnetic properties of CdS thin films were investigated. X-ray diffraction studies showed that the textures of all Cd1-xCoxS thin films were cubic with (1 1 1) preferred direction. It was determined from Scanning electron microcopy micrographs that grain size of the samples was found to be around 150 nm. Optical transmittance of the CdS thin films decreased from similar to 85% to similar to 65% with Co doping. It was observed from photoluminescence spectra that all samples had two broad peaks around 380-500 nm and 520-700 nm. The resistivity value of Co doped samples was higher than that of undoped CdS. The undoped and Co doped CdS thin films showed a ferromagnetic behavior at room temperature. (C) Elsevier B.V. All rights reserved.