Theory and empirical evidence generally credit children with creating stability in their parents’ marriages, but whether children have a similar effect on cohabiting unions has not been previously investigated in the United States. This article uses the National Survey of Family Growth (N = 2,716) to evaluate the effects of children on the stability of couples who cohabit. The article distinguishes between conceptions and births because the two have different implications for union stability. The results indicate that children conceived during cohabitation are associated with greater stability of their parents’ relationship, particularly for Whites and Latinos, whereas children conceived and born during cohabitation are not. In addition, the effect of children on couple stability depends on whether the couple is cohabiting or has transitioned into marriage.