Child maltreatment is a pressing concern in the United States, with more than four million children referred to child protective services in 2022. Parental mental health and substance use disorders are strongly associated with child maltreatment. We use administrative data from 2004–2022 to study the relationship between the number of mental health and substance use treatment centers and child maltreatment reports in U.S. counties. Findings show that a 9.6% increase in the supply of treatment centers per county reduces child maltreatment reports by 0.7% and child injury deaths by 0.4%. These findings suggest that improved access to mental health and substance use treatment may help reduce child maltreatment.