Family instability in the United States has increased dramatically since the 1970s. Demographic changes in family life including postponement of marriage, more short-term cohabiting unions, and a dramatic increase in the rate of births to unmarried parents, mean that considerable numbers of adults and children experience frequent relationship churning in their family lives. Family instability has been found to impede parenting practices, increase stress and mental health problems, reduce social support networks, and increase poverty and material hardship. Instability is also linked to many detrimental outcomes for children, including behavioral problems, reduced educational achievement and attainment, and health deficiencies. Some scholars have suggested that family instability, which is disproportionately concentrated among economically disadvantaged groups, may increase income inequality and contribute to the intergenerational transmission of poverty. Another recent demographic change in the United States— the rapid and dramatic rise in mass incarceration—may contribute to family instability. About 2.3 million U.S. residents (1 in every 134 individuals) are incarcerated in prisons or jails, and even larger numbers of individuals have been recently released back to their families and communities. There are compelling reasons to believe that mass incarceration, most often experienced by poorly educated minority men, contributes to family instability. Indeed, most of these men—prior to confinement, while behind bars, and after release—are connected to families as romantic partners and fathers. Incarcerated men are simultaneously members of and isolated from families, and are by and large unable to perform their roles as romantic partners and fathers. Maintaining contact with incarcerated partners is difficult and costly for women, while men, upon their release, may face a variety of consequences including stigma and discrimination, difficulty finding employment, and increased physical and mental health problems. All of these consequences could make reintegration into family life difficult. Despite considerable recent research on the effects of incarceration on family life more generally, as well as a vast literature documenting how marriage leads to a reduction in crime, there has been much less research on the consequences of incarceration for the dissolution of marital, cohabiting, and nonresidential romantic relationships. Given the considerable number of families affected by incarceration, the unequal distribution of incarceration across the population, and the potential consequences of family instability for the intergenerational transmission of inequality, understanding how the expanding penal system affects relationship dissolution is an important new area of research. I explore the possible connections in this article, examining analyses done using data from the Fragile Families and Child Wellbeing Study, a longitudinal survey of parents who share children. I consider three previously unexplored research questions that extend our knowledge about the collateral effects of incarceration on relationship dissolution. First, how is paternal incarceration associated with dissolution among couples that share children? Second, does this association vary by parents’ relationship status when their child was born? Third, to what extent do post-incarceration changes in family life (including relationship quality, economic wellbeing, and physical and mental health) explain the association between incarceration and relationship dissolution?