© 2016 Trans Tech Publications, Switzerland. Structural, morphological, optical and electrical properties of magnesium (Mg) doped zinc oxide (ZnO) films were prepared by the ultrasonic spray pyrolysis technique on a microscope glass substrate, and have been studied in terms of the Mg doping content. The precursor solutions of Mg doped ZnO films were prepared from zinc acetate dihydrate (Zn(CH 3 OO) 2 ·2H 2 O) and magnesium acetate tetrahydrate (CH 3 COO) 2 Mg·4H 2 O) as dopant. The compositions of these solutions were fixed at 0.02 M of Zn(CH 3 OO) 2 .2H 2 O and the atomic percentage ratio of Mg/Zn varied from 0 to 20 atomic %. The XRD patterns of all films showed ZnO hexagonal wurtzite structure and the morphology showed homogeneous structure/texture being pinhole-free with added Mg content. It was found that Mg2+ ions did not change conductivity of ZnO films due to the partial substitution of Zn2+ ion with the same valence Mg2+ ion. For optical properties, all films showed high transmittance over 80% and absorbance around 0.01 in the visible and near infrared regions. Moreover, the Mg dopant affects the shift of the absorption edge in the transmittance spectra of the films to a lower wavelength in the ultraviolet region and increases the band gap of the samples.