School-based mentoring programs are popular prevention programs thought to influence youth development; but rigorous evaluations indicate that these programs often have small effects on youth outcomes. Researchers suggest that these findings may be explained by (a) mentors and mentees failing to develop a close relationship and (b) mentors not setting goals or focusing on specific skills necessary to improve outcomes. We assessed these explanations using data from approximately 1,360 mentor and mentee pairs collected through a national study of school-based mentoring (called, ‘The Student Mentoring Program’). Specifically, we tested the influence of mentee-reported relationship quality and mentor-reported use of goal-setting and feedback-oriented activities on academic, behavioral, and social-emotional outcomes. Results suggested that youth reported relationship quality was associated with small to medium effects on outcomes. Moreover, goal-setting and feedback-oriented activities were associated with moderate to large effects on outcomes. We also found significant interactions between relationship quality and goal-setting and feedback-oriented activities on youth outcomes. We conclude that there appears to be a ‘sweet-spot’ wherein youth outcomes are maximized. The results of this study suggest a need for school-based mentoring programs to monitor and support mentors in developing a close relationship while also providing opportunities to set goals and receive feedback.