This article presents the results of a study on the effectiveness of Functional Family Therapy (FFT), a family intervention designed to prevent delinquency. The sample includes 155 court-involved youth. This study employs two complementary outcomes: court-obtained recidivism data and clinical therapeutic data, the Strengths and Needs Assessment (SNA). Adolescents in the treatment and in the comparison groups experienced statistically significant improvements in the majority of the SNA domains. Although youths in the treatment group improved more, the differences between the groups were not statistically significant. Multivariate analysis showed that youths in FFT had significantly lower odds of recidivism as measured by reconvictions for drug offences, property offences and technical violations. The results suggest that FFT was effective in reducing recidivism; however, such reductions cannot be attributed to improvements in the SNA scores.