Research on the relationship between political institutions and civil war has paid insufficient attention to the role of traditional institutions in developing countries. This study presents large-N evidence showing that traditional ethnic institutions with origins prior to Western colonization are associated with the prevalence of civil wars in Africa after independence. Matching ethnographic data on the pre-colonial political organization of African indigenous groups to contemporary data on ethnic groups in conflict, I investigate the relationship between the traditional organization of ethnic groups and ethnic civil wars in Africa after decolonization. Specifically, I argue that excluded groups with centralized traditional institutions can rely on these institutions to more credibly bargain with the state, and that this reduces their risk of conflict. Accordingly, I find that excluded groups with centralized pre-colonial institutions are less likely to be involved in civil wars.