This book is based on a study of the influence of the interpersonal dimension on the mentors' perception of the quality of their practice. The research drew on theoretical research literature that includes teacher's professional development and growth, adult learning, and interpersonal relationships. The research used a mixed methods approach, which integrated qualitative and quantitative methods of data collection. The findings of this research allow the construction of a new theory of mentoring which draws on interpersonal dimension theories, and adopts the perception of mentoring as a dual function role. The research suggests strengthening the mentors' interpersonal capacities through focusing mentor training and professional development frameworks on the development of the understanding of the interpersonal dimension in mentoring as well as on developing subject matter knowledge on an equal basis.