Objective: To identify the clustering of adverse childhood experiences (ACEs) that best characterize child welfare-involved children with known complex health concerns. Data source: Multi-informant data were obtained from Wave I of the National Survey of Child and Adolescent Well-Being (NSCAW II). Study design: This study used a cross-sectional design and classification and regression tree (CART) analyses. Data collection: Data were collected from families with children, aged birth to 17, investigated for child maltreatment and their child protective services caseworkers, including demographic characteristics of the children, their histories of adversity, and a wide range of health concerns. Principal findings: Results indicate that for children between the ages of six and 17, experiences of physical abuse alone, as well as experiences of physical abuse combined with having a caregiver with mental illness, are most strongly associated with complex health concerns. For children aged 2-5 years, results suggest that caregiver mental illness is a key adverse experience associated with complex health concerns. Conclusions: Identifying specific combinations of ACEs may be a critical next step for child- and youth-serving agencies to allow providers to better calculate risk of health problems among children exposed to adversity.