The study found that adolescents whose families participated in the Resourceful Adolescent Parent Program (RAP-P) alongside routine care showed greater reductions in suicidal behaviour and psychiatric disability compared with those receiving routine care alone. Improvements were maintained over follow-up and were accompanied by significant improvements in family functioning. Mediation analyses suggested that reductions in suicidal behaviour were largely explained by improvements in family relationships and communication. Overall, the findings provide promising evidence that strengthening family functioning may be an important mechanism for reducing suicidal behaviour in adolescents and support the value of family-based interventions in clinical practice.