The effects of residual stress and interface dislocations on the ionic conductivity of yttria stabilized zirconia (YSZ) polycrystalline nano-films deposited onto quartz substrate via pulsed-DC magnetron sputtering are systematically studied. The residual stress of YSZ film is evaluated by a cos(2 omega)alpha sin(2)psi method. The X-ray diffraction data indicates that a peening-induced compressive residual stress develops in the as-deposited film, increases with film thickness, and decreases the ionic conductivity. On the other hand, a thermal-mismatch-induced tensile residual stress develops in the annealed film, increases with annealing temperature, decreases with film thickness, and enhances the ionic conductivity. Ionic conductivities higher than the YSZ bulk are measured in both the as-deposited and annealed YSZ nano-films, indicating the existence of interface enhancement effect on the ionic conductivity. A type of low-energy dislocation structure forms next to the interface by sputtering, which hinders oxygen ion diffusion along the interface and lowers the ionic conductivity. (C) 2014 Elsevier B.V. All rights reserved.