The purpose of this paper is to examine the ways in which a school--university mentorship programme promotes a range of growth experiences, both negative and positive, for the participating mentor teachers. The paper presents a brief description of a school--university partnership, discusses the ways in which this partnership operates, summarises the literature on mentoring and explores the concepts of power and vulnerability as related to how the veteran teacher participants in the study perceive the benefits and challenges of mentoring. The authors argue that the nature of the Master of Education in Teaching programme, with its heavily based clinical component and expanded student-teaching experience, provides a distinctive magnifying lens of mentoring issues that is highly relevant for other professional teaching units who are considering using mentoring as a form of professional development for teachers. This study gives insight into the experiences of five mentor teachers so as to deepen understanding about mentoring as a complex and challenging form of professional growth and leadership for teachers.