Objectives: This review evaluates the evidence on the effects of functional family therapy (FFT) on drug abuse reduction for young people in treatment for nonopioid drug use. Data and Analysis: We followed Campbell Collaboration guidelines to conduct a systematic review of randomized and nonrandomized trials. Results: The search yielded two studies that met inclusion criteria. Only one study provided numerical results on the effect of FFT on drug use reduction. Conclusions: There is insufficient evidence to allow any conclusion to be drawn on the effect of FFT for young people in treatment for nonopioid drug use. There is a need for more research and particularly for more methodologically rigorous studies in the field of treatment for young drug users.