This report presents key findings from a mixed methods study examining how substance use affects child welfare systems across the country. The study combined statistical modeling and qualitative data collection which documented the perspectives and experiences of child welfare administrators and practitioners, substance use treatment administrators and practitioners, judges and other legal professionals, law enforcement officials, and other service providers. Results indicate that nationally, rates of drug overdose deaths and drug-related hospitalizations have a statistical relationship with child welfare caseloads (i.e., rates of child protective services reports, substantiated reports, and foster care placements). Generally, counties with higher overdose death and drug hospitalization rates have higher caseload rates. In addition, these substance use indicators correlate with rates of more complex and severe child welfare cases. Several major challenges affect how child welfare agencies and families interact with substance use treatment options, including medication-assisted treatment for opioid use disorder. Family-friendly treatment options are limited, and caseworkers, courts, and other providers often misunderstand how treatment works and lack guidelines on how to incorporate it into child welfare practice. Child welfare agencies and their community partners are struggling to meet families needs. Haphazard substance use assessment practices, barriers to collaboration with substance use treatment providers and other stakeholders, and shortages of foster homes and trained staff undermine the effectiveness of agencies responses to families. The report includes discussion guides for child welfare administrators and practitioners, substance use treatment administrators and practitioners, and other administrators and practitioners. (Author Abstract Modified)