Using data collected from 10,511 kindergarten children and their parents from the Early Childhood Longitudinal Study-Kindergarten Cohort, this study examines child well-being across cohabiting 2-biological-parent families; cohabiting stepfamilies; married stepfamilies; and married 2-biological-parent families. Findings indicate no differences in child well-being for children living in cohabiting stepfamilies and cohabiting 2-biological-parent families. Multivariate models controlling for child characteristics, economic resources, maternal depressive symptoms, stability, and parenting practices show no significant differences across family types in child well-being indicators, with the exception of reading skills. Important factors in explaining the link between cohabitation and child well-being include economic resources, maternal depressive symptoms, and parenting practices.