While the majority of STEM persistence has focused on outcomes for first-year students, there has been little investigation into the outcomes for peer mentors. Of the studies conducted, results are promising. Benefits for peer mentors include a change in their perceptions on teaching and learning; an improvement in their communication, presentation, and leadership skills; and an increase in their understanding of the course content. However, one of the main limitations of these studies is their small sample sizes. Many of the studies purport sample sizes of 5 to 30 peer mentors. The purpose of this article is to overview, from the perspective of the mentors, a university-wide interdisciplinary peer mentoring program for first-year students enrolled in key gateway courses (Calculus I, Physics I, and Chemistry I). Each year over 1,000 undergraduate students participated in the program and were served by approximately 136 peer mentors. The program was monitored by an advisory committee comprising an interdisciplinary team of faculty, university staff, program staff, and an outside consultant. This article examined mentor outcomes and included the data from over 300 mentors.