In this study, we model the core structure of screw dislocations with [1 0 0] and [0 1 0] Burgers vector in MgSiO3 perovskite, in the pressure range of Earth's lower mantle (25–130 GPa). We use a generalized Peierls–Nabarro model, called Peierls–Nabarro–Galerkin, based on generalized stacking-fault energy calculations. These stacking-fault energy calculations are performed using a pairwise potential parametrization and compared to ab initio results. The results of Peierls–Nabarro–Galerkin calculations demonstrate that [1 0 0] dislocation and [0 1 0] are, respectively, characterized by a planar core spreading in (0 1 0) and (1 0 0). Our results emphasize the role of [1 0 0](0 1 0) and [0 1 0](1 0 0) slip systems in the deformation mechanism of MgSiO3 perovskite. Furthermore, we validate the use of pairwise potential for further dislocation modelling of such minerals at the atomic scale.