East Asia has a long history of genocide and mass atrocities. For much of the Cold War, East Asia was one of the world's most violent regions, experiencing multiple outbursts of mass killing. Since the end of the Cold War, however, the region has been transformed thanks to another Asian miracle. There are now fewer cases of genocide and mass atrocities in East Asia today than at any point in history for which we have reliable records. This article demonstrates and then tries to account for the dramatic decline of mass atrocities in East Asia. It argues that the decline was enabled by a combination of three major structural changes: reduction in the selection of mass atrocities as a weapon of war, increase in incomes, and progress towards democratization combined with the emergence of new ideas about sovereignty and their accommodation with existing principles of non-interference. Together, these structural and ideational changes created a changed regional context of increased costs and reduced payoffs for the commission of mass atrocities.