We publish in Scientific Reports an original study on the prediction of mechanical twinning in MgSiO3 post-perovskite, known to be an important constituent at the core mantle boundary. Being a few hundreds of kilometers thick, the D’’ layer located just oabove the core mantle boundary is characterized by an important seismic anisotropy. In this article, based on first-principles calculations, we demonstrate the occurrence of mechanical twinning in post-perovskite structure and predict the mechanical behavior of twin nucleation. As twinning involves changes in crystal orientation, such mechanism may potentially influence the development of crystal preferred orientations. The future incorporation of this twinning mechanism in seismic anisotropy model should lead to a novel understanding of the origin of seismic anisotropy at the core mantle boundary.