Humanitarian assistance is intended to ameliorate the human costs of war by providing relief to vulnerable populations. Yet, the introduction of aid resources into conflict zones may influence subsequent violence patterns and expose intended recipients to new risks. Herein, we investigate the potential negative externalities associated with humanitarian aid. We argue that aid can create incentives for armed actors to intentionally target civilians for violence. Aid incentivizes rebel violence by providing opportunities for looting and presenting challenges to rebel authority. It potentially incentivizes state violence where it augments rebel capabilities or provides rebels a resource base. We evaluate both arguments using spatially disaggregated data on aid and conflict violence for a sample of nearly two-dozen post-Cold War African countries. The results of multiple statistical analyses provide strong support for the argument that humanitarian aid is associated with increased rebel violence but less support for the relationship between aid and state violence.