Background: Parents and children are close over the life course. However, these relationships often change as parents age and children enter adulthood. Today, the entrance into adulthood for children has become delayed and increasingly unstable. Such changes may interrupt the child’s acquisition of resources used to support themselves and their midlife parents, having implications for parents’ mental and physical health. The purpose of this study is to examine the role of adult children’s transitions to adulthood on parents’ mental and physical health. Methods: Using data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) and the Add Health Parent Study (AHPS), we investigated how certain transitions to adulthood (e.g., education, marriage, residential independence, employment, parenthood, and incarceration) for children were linked to the mental and physical health of their midlife parents. Results: In sum, we found that children’s educational attainment was linked to fewer activities of daily living (ADL) limitations and depressive symptoms among parents. Children’s marriage and employment were also associated with fewer ADL limitations among parents. Conclusions: Our findings reveal that adult children’s circumstances are associated with the mental and physical health of their midlife parents.