Abstract The transparent conductive and flexible Mg and Ga co-doped ZnO (MGZO) thin films were prepared on poly-ethylene telepthalate (PET) by the RF magnetron sputtering technique at room temperature. The effects of different thicknesses on the structural, chemical, morphological, optical and electrical properties of MGZO thin films were investigated. X-ray diffraction studies showed that MGZO thin films were grown as a polycrystalline hexagonal wurtzite phase without a secondary phase. The peak intensities for the (0002) plane of MGZO thin films were enhanced with increasing thickness. A typical survey spectrum of MGZO thin films confirmed the presence of Mg, Ga, Zn and O resulting from MGZO films regardless of thickness. The MGZO thin films had a larger grain size with increasing thickness. The MGZO thin films showed the widest optical band gap energy of 3.91 eV (50 nm) and lowest electrical resistivity of 5.76 × 10 −3 Ω cm (400 nm).