Transparent conducting aluminum doped cadmium oxide (CdO:Al) thin films were deposited by spray pyrolysis method on glass substrates for various concentrations of aluminum (1-5 wt.%). CdO:Al films were characterized using different techniques such as X-ray diffraction (XRD), atomic force microscopy, optical transmittance and Hall measurement. XRD analysis showed that CdO films exhibit cubic crystal structure with (2 0 0) preferred orientation. A minimum resistivity of 3.4 x 10(-4) Omega cm with carrier concentration of 4.12 x 10(20) cm(-3) is achieved when the CdO film is doped with 3 wt.% Al. The band gap value increases with doping and reaches a maximum of 2.53 eV when doping level is 3 wt.% and then decreases for higher Al doping concentration. (C) 2010 Elsevier B.V. All rights reserved.