A burgeoning literature considers the consequences of mass imprisonment for the well-being of adult men and—albeit to a lesser degree—their children. Yet virtually no quantitative research considers the consequences of mass imprisonment for the well-being of the women who are the link between (former) prisoners and their children. This article extends research on the collateral consequences of mass imprisonment by considering the association between paternal incarceration and maternal mental health using data from the Fragile Families and Child Wellbeing Study. Results show that recent paternal incarceration increases a mother’s risk of a major depressive episode and her level of life dissatisfaction, net of a variety of influences including prior mental health. The empirical design lends confidence to a causal interpretation: effects of recent incarceration persist even when the sample is limited to mothers attached to previously incarcerated men, which provides a rigorous counterfactual. In addition, the empirical design is comprehensive; after isolating key mechanisms anticipated in the literature, we reduce the relationship between recent paternal incarceration and maternal mental health to statistical insignificance. These results imply that the penal system may have important effects on poor women’s well-being beyond increasing their economic insecurity, compromising their marriage markets, or magnifying their risk of divorce.