We conduct a comprehensive examination of the causal effect of charter schools on school segregation, using a triple differences design that utilizes between-grade differences in charter expansion within school systems, and an instrumental variable approach that leverages charter school opening event variation. Charter schools increase school segregation for Black, Hispanic, White, and Asian students. The effect is of modest magnitude; segregation would fall 6 percent were charter schools eliminated from the average district. Analysis across varied geographies reveals countervailing forces. In metropolitan areas, charters improve integration between districts, especially in areas with intense school district fragmentation.