Charter schools have been one of the most important dimensions of recent school reform measures in the United States. Currently, there are more than 5,000 charter schools spread across forty U.S. states and the District of Columbia. Though there have been numerous studies on the effects of charter schools, these have mostly been confined to analyzing their effects on student achievement, student demographic composition, parental satisfaction, and the competitive effects on regular public schools. This study departs from the existing literature by investigating the effect of charter schools on enrollment in private schools. To investigate this issue empirically, we focus on the state of Michigan, where there was a significant spread of charter schools in the 1990s. Using data on private school enrollment from biennial National Center for Education Statistics private school surveys, and using a fixed-effects as well as instrumental-variables strategy that exploits exogenous variation from Michigan charter law, we investigate the effect of charter school penetration on private school enrollment. We find robust evidence of a decline in enrollment in private schools—but the effect is only modest in size. We do not find evidence that enrollments in Catholic or other religious schools suffered more relative to those in nonreligious private schools.