Undergraduate academic peer mentors gain a deeper understanding of the academic content and develop professional teaching and coaching skills. While the value of this high impact practice is well documented for academic outcomes, little is known about the leadership self-efficacy that results from serving as an academic peer mentor. In this initial quantitative study of a cross-disciplinary academic peer mentoring program for 79 American undergraduates, we found that after serving as an academic peer mentor, students reported higher self-efficacy for leading groups. Academic peer mentorship programs show promise as a leadership development opportunity for college students.