This paper provides novel evidence on the causal effects of juvenile incarceration on long-run labor market outcomes and family spillovers. We link criminal justice records from South Carolina to rich socioeconomic data and exploit quasi-random assignment of defendants to judges with varying incarceration propensities in an instrumental variables framework. Juvenile incarceration reduces earnings and employment during early adulthood for males. These earnings losses appear to operate primarily through reduced educational attainment, changes in mental health and behavior, and societal stigmatization, with adult incarceration having a modest role. For females, our analyses suggest that juvenile incarceration significantly increases earnings. These divergent gender effects can potentially be explained by a large reduction in teenage and early-adulthood fertility, which, in turn, may increase female labor market attachment. Finally, we document negative family spillover effects: connected children in the household experience lower educational attainment, suggesting that the broader social costs of juvenile incarceration may be larger than previously recognized.