Objective: Client-informed outcome feedback has consistently been shown to enhance psychotherapy outcomes for adults, particularly for clients at risk of treatment failure. However, there is a paucity of studies examining feedback in youth psychotherapy. Specifically, there is no research examining the feedback effect of the Youth-Outcome Questionnaire [Burlingame, G. M., Wells, M. G., & Lambert, M. J. (1996). The youth outcome questionnaire. Stevenson, MD: American Professional Credentialing Services.], despite the dominance of the adult version of the measure (Outcome Questionnaire-45 [Lambert, M. J., & Burlingame, G. M. (1996). Outcome questionnaire 45.2. Wilmington, DE: American Professional Credentialing Services.]) in adult feedback studies. Method: The effectiveness results for adult (N = 398) and youth clients (N = 397) attending psychotherapy at two psychology training clinics are presented and benchmarked against treatment-as-usual (for adults and youth) and feedback (for adults). Results: Psychotherapy with a feedback-informed approach was more effective than treatment-as-usual benchmarks, with 50% of adults and 64% of youth significantly improving after psychotherapy. Rates of adult improvement were similar to feedback-informed benchmarks, although the current sample had a higher rate of deterioration. There are no previously identified feedback-informed benchmarks for the Y-OQ, making this sample the first benchmark for future studies. Conclusions: Results support the benefits of feedback at enhancing psychotherapy outcomes for adults, and replicate this finding in a youth sample. Results also replicate that trainee psychotherapists can be as effective as licenced psychotherapists.