We present Molecular Dynamics (MD) simulations of the shear–coupled migration behaviour of a Σ 17(530)/ symmetrical tilt boundary, in the absence or in the presence of nanocracks lying on the grain boundary (GB) plane. The simulations have been performed for copper bicrystals at 300 K. Shear–coupled migration (SCM) occurs in both simulated configurations. For the case of a tilt boundary without nanocracks, the observed results are similar to the ones reported elsewhere. However, for the case of the Σ 17(530) boundary presenting nanocracks, SCM takes place ahead of the mode II loaded crack tips, but the GB gets pinned by the crack tip. The bulging of the tilt boundary reduces the shear stress on the boundary surface near the tip and hinders mode II crack propagation. The applied stress grows until other deformation mechanisms, such as emission of dislocations from the crack tip vicinity or GB sliding, are activated.