ABSTRACTMg doped ZnO thin films were prepared by DC/RF magnetron co-sputtering in (Ar+O₂) ambient conditions using metallic Mg and Zn targets. We present a comprehensive study of the effects of film thickness on the structural, optical and magnetic properties. Room temperature ferromagnetism was observed in the films and the saturation magnetization (M_S) increases at first as the film’s thickness increases and then decreases. The M_S value as high as ∼15.76 emu/cm³ was achieved for the Mg-doped ZnO film of thickness 120 nm. The optical band gap of the films determined to be in the range 3.42 to 3.52 eV.