Study objectives were to (a) understand juvenile justice staff members' experiences with engaging families in youth substance use services and (b) identify staff-perceived barriers to family engagement across steps of substance use service provision. Lack of family involvement in juvenile justice system substance use (SU) services is a key barrier to successful treatment of justice-involved youth. From June through November 2015, 33 focus groups were conducted at juvenile justice system probation sites across seven states. There were 263 participants, which included juvenile justice probation and behavioral health staff. Strategies to engage families in services were highly variable across the 33 juvenile justice sites. Juvenile justice staff members identified barriers to family engagement in SU services including family discomfort, distrust of juvenile justice staff, lack of family service compliance, difficulties accessing SU services, lack of transportation, insurance and cost barriers, low perceived need for treatment, lack of SU education, and SU treatment stigma. Barriers to family engagement directly impact the success of SU service provision in juvenile justice settings. Implementation of strategies to engage families of justice-involved youth (e.g., providing tangible, informational, and emotional support to families, and involving families in juvenile justice policy and care decisions) are critical to improving SU outcomes among this vulnerable population.