In this three-year qualitative study we investigated the experiences and perspectives of university undergraduate students who were peer mentors for students with intellectual and developmental disabilities (ID/DD) in a postsecondary education certificate program at a public university in the northeastern United States. The findings were categorized into three major themes: (a) the roles of these peer mentors; (b) the benefits and challenges related to peer mentoring; and (c) the transformative effect of peer mentoring on these undergraduate students. Findings provide insights into postsecondary education for students with ID/DD and suggest implications for (a) parents of students with ID/DD, (b) transition from high school, and (c) administrators at institutions of higher education.