Widespread rotations of maximum compressive stress in the upper crust are revealed in eastern Tibet by the focal mechanism stress inversion technique. Because of the good correlation with locations of folds, anticlines, and mountains in the region, the upper crustal stress variation is related to the lateral displacement of upper crust. To compare deformations in upper crust and upper mantle, we use SKS/SKKS splitting measurements to investigate the seismic anisotropy in eastern Tibet. The fast polarization directions subparallel to the strikes of faults in Chuandian fragment and southern boundary tectonic belt. This may indicate that the induced anisotropy mainly resulted from alignment of fault fabrics by strong shearing along strike‐slip faults, while the widespread stress rotations and systemic angular difference between upper crustal stress field and seismic anisotropy suggest that the decoupling of upper crustal deformation from middle‐lower crust by a series of detachments in the process of the crust thickening resulted from the obstruction of eastward expansion by Sichuan Basin.