Ultrafine-grained Pd specimens with a mean grain size of 130 nm were compressed by 10% in a scanning electron microscope and the strain-induced change in orientations of grains was measured by in-situ electron-backscattering diffraction. A comparison of grain orientations before and after compression straining revealed substantial grain rotations. The analysis of the results performed using polycrystal plasticity simulation showed that the variation of orientations with strain cannot be explained only by crystallographic dislocation slip. A large portion of strain is proved to be accommodated via cooperative non-crystallographic grain rotation.