Boulders are frequently observed to cluster around planetary impact craters, yet the physical origin of these spatial patterns remains unclear. Using controlled granular impact experiments, we demonstrate that crater-associated boulder fields can emerge from the interactions between the expanding fine-grained ejecta and pre-existing boulders on the target surface. The impact drives boulders radially outward, which results in clustering of boulders around the crater, characterized by a density peak at a finite distance from the crater rim followed by a gradual decrease in boulder density with radial distance. The location of this peak scales with impact energy according to the same one-quarter power law as the crater diameter, providing a link between the boulder redistribution and the crater-formation. Measurements of individual boulder trajectories further show that the peak boulder velocity decays rapidly away from the crater rim, such that distal boulders are only weakly mobilized. These findings highlight the potential role of impact-driven redistribution of pre-existing boulders in shaping their spatial distribution around impact craters and provide insight into particle transport in heterogeneous granular media.