Aims: To determine whether family and parenting interventions benefit children and adolescents with conduct disorder and delinquency. Methods: Meta-analysis of eight randomised controlled trials involving 749 children and adolescents (aged 10-17 years) with conduct disorder and/or delinquency. Criminality, academic performance, future employment, problem behaviour, family functioning, parental mental health, and peer relations were evaluated. Results: Family and parenting interventions significantly reduced the time spent by juvenile delinquents in institutions (weighted mean difference 51.34 days). There was also a significant reduction in the risk of a juvenile delinquent being rearrested (relative risk 0.66) and in their rate of subsequent arrests at 1-3 years (standardised mean difference -0.56). Conclusions: The evidence suggests that family and parenting interventions for juvenile delinquents and their families have beneficial effects on reducing time spent in institutions and their criminal activity. In addition to the obvious benefit to the participant and their family, this may result in a cost saving for society.