Stresses in zinc oxide (ZnO) films prepared by radio frequency (rf) magnetron sputtering have been studied using a bending beam technique. The stresses exhibited at room temperature have been found to be strongly substrate dependent. The films deposited on gallium–arsenide (GaAs) substrates have exhibited much less compressive stress than those on silicon. This was contrary to what was expected. This may be attributed to: as revealed by x‐ray diffraction experiments, the films grown on GaAs are less crystalline so that peening effect could occur less intensively during deposition. The stress varies with different processing conditions, especially substrate temperature and total gas pressure.