Families in the United States are increasingly diverse, which has given rise to questions about the consequences these new family forms have for children’s outcomes. This study uses a life course perspective to examine the association between family transitions, nontraditional family structures (with particular attention to same-sex parent families), and children’s psychosocial well-being. The Early Childhood Longitudinal Study–Kindergarten cohort was used to examine children’s externalizing well-being, internalizing well-being, and interpersonal skills. Results indicate that nontraditional family structures are associated with poorer psychosocial well-being, but this is largely accounted for by changes and transitions experienced in the creation of new families. The findings provide a critical look at the assumptions embedded in arguments focused solely on family structure, and joins other research in calling attention to the importance of family processes for understanding the well-being of children.