The ZnO: Al thin films were exposed to beta radiation at 0.65 kGy absorbed dose level using a Sr-90 radioisotope after the thin films derived by sol gel dip coating technique were annealed in the argon at 700 degrees C. The optical changes in the thin film were determined for the unirradiated and the irradiated states at four different Al concentrations (0.8, 1.0, 1.2 and 1.6 at.%). There was a relation between brightness and light reflectance in the ZnO: Al thin film. The characterization of the colour parameters was specified for the unirradiated and the irradiated states according to the standardization concept. Beta irradiation caused to changes in the electrical resistivity, the light absorbance, the brightness and the colour parameters with the slight variations of the grain height on surface of the film. The absorbed dose caused a slight decrease in the grain height of the ZnO: Al thin film after the irradiation. Besides, the surface roughness of the irradiated film increased slowly as the result of the agglomeration tendency on the surface of the film.