This study investigated whether providing client feedback data to supervisors for use in supervision would influence supervision and counselor self-efficacy. Trainees were assigned to either a continuous feedback condition, where feedback was provided to supervisors, or a no-feedback condition. Results showed that trainees in both conditions improved client outcomes over the year, but those in the feedback condition improved more. However, ratings of supervisory alliance and satisfaction did not differ between conditions. The relationship between counselor self-efficacy and outcomes was stronger for those in the feedback condition, suggesting feedback may facilitate a more accurate assessment of skills.