We investigated the effects of thickness on the electrical, optical, structural and morphological properties of B and Ga co-doped ZnO (BGZO) films grown by radio frequency (RF) magnetron sputtering. All the prepared BGZO films showed preferentially c-axis orientation and structure of hexagonal wurtzite. The results also indicated that with an increase in film thickness, the crystallite sizes of the films were increased and the optical band gap (Eg) was decreased. Below a critical thickness of about 210nm, the thickness of the BGZO films significantly affected the electrical properties of the films. The average transmittance for all the grown films did not change obviously with the thickness.