The authors of this article report the results of a mentorship-based professional development intervention study grounded in the induction and mentoring literature. The purpose of this study was twofold. First, the study aimed to determine how mentorship-based professional development influenced mentors' self-rated competence of mentoring; the second goal was to analyze changes in newer teachers' thinking about teaching and the mentoring experience. Two groups of teachers participated in the project: 15 experienced teachers learned to be mentors for 15 newer physical education teachers who volunteered to learn and be mentored. The authors hypothesized that the mentorship-based professional development project would increase mentors' self-reported competence in mentoring abilities and lead to positive outcomes in the newer teachers' thinking about teaching and the mentoring experience. This project was an attempt to address the gap in the research related to teachers mentoring other teachers in the development of curricular expertise. In this study experienced teachers were provided with a range of professional development activities focused on developing mentoring skills. These activities were guided by the principles of adult learning theory (e.g., Knowles, Holton & Swanson, 1998), which focused on the active, collaborative, and use-based approach to learning. This approach was different from traditional approaches to children's learning, which is often presented from a content perspective. Adult learning is most effective from a process perspective when learners are included in the planning and implementation of educational programs. The study reported here focuses on the impact of this mentoring process. (Contains 1 table and 2 figures.)