AbstractHere we investigate the effects of damage fault zones on rupture propagation by conducting a series of 3‐D dynamic rupture simulations on a planar vertical strike‐slip fault. We find that damage fault zones can promote rupture extent and increase earthquake potency. The waves reflected from the bottom of shallow damage fault zones can increase shear stress on the fault and thus promote rupture propagation. In addition, the promotional effects increase with the width and depth extent of damage fault zones. The overall effects of the waves reflected from the fault‐parallel side boundaries of damage fault zones are unfavorable for rupture propagation. Therefore, rupture propagation is promoted with the increased width of fault zones due to geometrical spreading effects. Moreover, nonground‐breaking ruptures may reach the ground surface with the effects of damage fault zones. Furthermore, along‐strike segmented fault zones as suggested by observations could also promote ruptures and may lead to preferred rupture directions if epicenters are close to fault zones. The effects of damage fault zones on rupture propagation hold important implications on assessing earthquake risk.