The current US undocumented population is large and settled. As a result, millions of US-born citizens are growing up with undocumented parents or siblings. In this paper, we use original survey data to study the politics of the US-citizen offspring of undocumented migrants. We test theories of parental political socialization, which imply that having undocumented parents may have chilling effects on political engagement. We also test theories of social activism, which predict that the offspring of the undocumented may be motivated to make use of their rights as US citizens by protesting on behalf of their parents. We find no evidence of lower political engagement among those with undocumented parents. Instead, we find that the offspring of the undocumented are more likely to protest on immigration issues, and more optimistic that popular protest can induce political change. We use an instrumental variables design to test whether these differences warrant a causal interpretation, and find tentative evidence that having undocumented parents does indeed have mobilizing political effects.