PurposeThis article aims to present a unique dimension to mentor studies in that unlike most research that focuses on the novice-teachers-mentee, this study explores the influence of mentoring on the mentors themselves. Two main questions were examined: “Which components of mentoring influence the mentors' professional development?” and “What is the differential impact of each of these components as they are internalized by the mentors?”Design/methodology/approachA total of 765 mentors completed a questionnaire composed of 47 multiple-choice questions and an open-ended question describing the contribution of mentoring. The survey thus generated both quantitative and qualitative data.FindingsThe results show three main components of mentoring that influence mentors' professional development in the following order: personal–emotional, didactic knowledge and systemic–organizational. The findings also illustrate how the mentors used a comparison process to develop their professional perception: first, by comparing their role as a teacher and their role as a mentor, and second, by comparing their own professional identity as a teacher with that of the novice-teacher.Research limitations/implicationsThe implications of the study point to the importance of mentoring for mentors' professional development. Practical implications of this study encourage mentor training courses that combine a body of knowledge of theory and practice, as well as supervision and mentoring for mentors. It may be important for mentors to develop a professional identity as mentors that is distinct from their professional identity as teachers.Practical implicationsThe implications of the study point to the importance of mentoring for mentors' professional development. Practical implications of this study encourage mentor training courses that combine a body of knowledge of theory and practice, as well as supervision and mentoring for mentors. It may be important for mentors to develop a professional identity as mentors that is distinct from their professional identity as teachers.Originality/valueThe manuscript attempts to explore the dynamic relationships within the mentoring process by investigating how mentoring impacts the development of mentors. It presents insights into the benefits of mentoring novice-teachers for the mentors themselves via analysis of a large-scale, nationwide study.