BackgroundChild maltreatment and polyvictimization are known risk factors for long-term detrimental health and development outcomes, including behavioral health challenges. However, effects from specific types and combinations of maltreatments are unclear. This study examined the association between maltreatment or polyvictimization and behavioral health in a child welfare sample. Participants and settingMedical records of children with child welfare involvement with at least one behavioral health condition (i.e., mental, behavioral or neurodevelopmental disorder, ICD-10 F01-F99) between 1/1/2018–12/31/2021 were extracted from a large, academic hospital system. MethodsBehavioral health complexity was categorized as non-chronic, non-complex chronic, or complex chronic using the Pediatric Medical Complexity Algorithm. Partial proportional logistic regression models adjusted for age, sex, race/ethnicity, caregiver type, and physical health complexity generated odds of behavioral health complexity by maltreatment type (physical abuse, sexual abuse, neglect) and maltreatment combinations. ResultsThe analytic sample included 3992 participants (mean age 7.6 (Standard Deviation, 5.0) 44 % female, 29 % white, 32 % black, 22 % Hispanic). Participants who experienced physical abuse (Odds Ratio [OR]: 1.79, 95 % Confidence Interval [CI]: 1.10–2.91), or neglect (OR: 1.69, 95 % CI: 1.38–2.07) were more likely to have increasing behavioral health complexity versus those without maltreatment. Participants with both physical abuse and neglect were over twice as likely (OR: 2.44, 95 % CI: 1.88–3.16) to have increasing behavioral health complexity versus those who did not experience maltreatment. ConclusionResults emphasize the differential impacts of maltreatment and polyvictimization exposures on behavioral health complexity among children with child welfare involvement that can guide risk assessment and clinical care.