Cobalt oxide thin films with variable thickness were deposited by pneumatic spray pyrolysis technique (PSPT) onto the amorphous glass substrates kept at 300 degreesC. The quantity of cobalt chloride solution was varied to obtain cobalt oxide thin films with thickness ranging from 0.9 to 1.7 mum. The effect of film thickness on structural, electrical and optical properties was studied. The X-ray diffraction (XRD) studies revealed that the crystallinity of the cobalt oxide film ameliorates with film thickness. Consequently, the room temperature electrical resistivity of the film decreases from 2.1 x 10(4) to 9 x 10(2) Ohm cm with increase in film thickness. Optical absorption studies reveal that cobalt oxide thin films exhibit optical transition by both the direct and indirect transitions.