The Cd 1−x Co x S (x = 0.00, 0.10, 0.20 and 0.40) thin films were deposited onto the glass substrate at a temperature of 523 K using a low cost spray pyrolysis technique. The SEM images show that the grain size and the roughness of the films were increased with increasing Co doping concentration. The as-deposited films were amorphous in nature but the annealed samples had a crystalline wurtzite hexagonal structure and the estimated average grain size lay in the range of 7 to 49 nm. The optical band gap of the films was decreased from 2.54 to 2.40 eV. The conductivity and activation energy of the films were decreased with increasing Co content but all the films showed semiconducting behaviour in the measured temperature range.