M measurements were made on textured PZT thin films excited by a 1 V rms in the presence of various DC biasing voltages. Apparent domain pinning sites were found in the films. All sites were located at grain boundaries and were coincident with abnormally large piezoelectric displacements in the film. Different sites were associated with domains aligned toward the free surface of the film and with those aligned toward the substrate. Finite element calculations used to determine residual stress as a function of grain-to-grain misorientation showed that large residual stresses and normal strains would be generated at grain boundaries for specific grain misorentations. Pinning sites in PZT thin films are interpreted in terms of residual stresses at grain boundaries due to grain-to-grain misorientation.