Few inquiries have investigated master's students in education as they mentor preservice teachers. In this embedded case study I explored the professional development of 15 master's students as they mentored 35 preservice teachers for eight weeks in a summer literacy camp. Data sources were e-mail exchanges, written reports, and transcriptions from focus groups and in-class conversations. I analyzed the data through constant comparison methods and discovered that the mentors were initially frustrated with their mentoring responsibilities and had little empathy for the preservice teachers. By the end of the camp, they recognized the benefits of mentoring and gained confidence as mentors. Learning occurred for both the mentors and the preservice teachers. Implications include the power of social participation in authentic contexts.