A systematic review of published and unpublished English language articles identified 14 studies containing 18 comparisons between functional family therapy (FFT) and another condition in the treatment of adolescent disruptive behavior and substance use disorders. In 11 of these comparisons, assignment to conditions was random, while nonrandom assignment occurred in seven studies. For both random and nonrandom comparisons, separate meta-analyses were conducted for subgroups of studies depending on the type of comparison group used. Data from studies of untreated control groups (CTL), treatment as usual (TAU), and well-defined alternative treatments (ALTs) were analyzed separately. Effect sizes from these six meta-analyses were as follows: random assignment FFT versus CTL (k = 3, d = 0.48, p < .01); random assignment FFT versus TAU (k = 3, d = .20, ns); random assignment FFT versus ALT (k = 5, d = .35, p < .05); nonrandom assignment FFT versus CTL (k = 2, d = .90, ns); nonrandom assignment FFT versus TAU (k = 2, d = .08, ns); and nonrandom assignment FFT versus ALT (k = 3, d = .75, p < .001). These results provide support for the effectiveness of FFT compared with untreated controls and well-defined ALTs, such as cognitive behavior therapy, other models of family therapy, and individual and group therapy for adolescents.