A growing body of research reveals a connection between maternal incarceration and various child development outcomes. Even so, little is known about how the timing of maternal incarceration may shape the social-emotional development of young children and the role of maternal mental health in mediating this association. Using a sample of 1097 mothers (18-52 years old, 47.6% white) and children (aged 12-48 months) receiving home visiting services in Wisconsin, this study examined the intergenerational effect of incarceration before a child's birth on child social-emotional development, and whether this association was mediated by maternal mental health. While incarceration prior to a child's birth was not directly associated with child social-emotional outcomes, path analysis revealed an indirect association between mother's incarceration prior to a child's birth and child social-emotional problems through maternal mental health problems. Findings suggest that formerly incarcerated mothers may experience long-lasting mental health concerns that can undermine child social-emotional development. To optimize outcomes, practitioners may consider services that address the mental health, social support, and instrumental needs of mothers and children who have been impacted by mass incarceration.