Peers have a prominent place within peer-mediated interventions (PMI). Understanding how they might benefit from their experiences supporting students with disabilities is an emerging area of much-needed research. This qualitative study was designed to identify the breadth of ways peers report being affected by their diverse experiences. We held eight focus groups with 41 secondary and postsecondary peers involved in PMIs alongside students with intellectual and developmental disabilities. They described nine distinct areas of impact: social impact, personal growth, changes in views, rewarding impact, skill development, advocacy, future intentions, academic impact, and negative impact. We provide recommendations for research and practice aimed at understanding the reciprocal impact of these widely advocated interventions.