Low-income U.S. households are increasingly burdened by unaffordable debt, with profound long-term economic and health consequences. Households of color are disproportionately negatively affected. This article examines the nexus of this rising indebtedness and mass incarceration through the experiences of a particularly marginalized group, people with mental illness. Drawing on qualitative research with 31 individuals with mental illness and recent incarceration in the city of New Haven, Connecticut, we show how carceral institutions and predatory financial practices intersect to create complex entanglements for poor and vulnerable people. While a growing body of scholarship focuses on criminal justice fines and fees, we highlight other types of debt that add to the overall burden, describing how incarceration deepens people’s existing debts of poverty and adds new debts from in-prison costs and identity theft. After release, those debts complicate the search for housing, employment, and financial stability, leading to further debt, stressing social relationships and reproducing social and economic inequality. The experiences of people with mental illness illuminates structures of marginalization and disadvantage that affect many others involved with the criminal justice system.