This article evaluates the effect of territorial autonomy on the outbreak of internal conflict by analyzing ethnic groups around the world since WWII. Shedding new light on an ongoing debate, we argue that the critics have overstated the case against autonomy policies. Our evidence indicates that decentralization has a significant conflict-preventing effect where there is no prior conflict history. In postconflict settings, however, granting autonomy can still be helpful in combination with central power sharing arrangements. Yet, on its own, postconflict autonomy concessions may be too little, too late. Accounting for endogeneity, we also instrument for autonomy in postcolonial states by exploiting that French, as opposed to British, colonial rule rarely relied on decentralized governance. This identification strategy suggests that naïve analysis tends to underestimate the pacifying influence of decentralization.