This study is the first formal, quantitative investigation of the effectiveness of Immunity-to-Change coaching for leadership development. Forty-five supervisors who engaged in Immunity-to-Change coaching were compared with a comparison group of 25 supervisors from the same company to determine whether coached participants reported more progress on their leadership development goals than did comparisons. Coached participants indicated their likelihood of using Immunity-to-Change tools to pursue further goals and identified the coaching components they found most useful. Extensive analyses revealed that the coached group reported significantly more progress toward their leadership development goals than their comparison group counterparts. Accordingly, a vast majority of coached participants indicated intent to use Immunity-to-Change coaching tools again in the future, especially the four-column map. These findings suggest that Immunity-to-Change coaching may be an effective intervention for corporate employees seeking to make progress on their leadership development goals.