This study examined the influence of treatment motivation on posttreatment effectiveness of an outpatient, individual social skills training for juvenile delinquents imposed as a penal sanction. Propensity score matching was used to match a control group of juveniles receiving treatment as usual (n = 108 of total N = 354) to a treatment group of juveniles receiving Tools4U, a social skills training with a parental component (N = 115). Treatment motivation was examined as a moderator and predictor of treatment effects on impulsivity, social perspective-taking, social problem-solving, lack of critical reasoning, developmental task-related skills, and parenting skills. Treatment effects were mostly consistent across juveniles with different levels of treatment motivation. Only one moderating effect was found on active tackling (i.e., actively addressing problems), and predictive effects were found on seeking social support, cognitive empathy, hostile intent attribution, and self-centeredness. Implications for further research are discussed.