The role of university-based mentors providing support for pre-service teachers (PSTs) on professional experience placements has long been an element of teacher education programs. These mentors often face challenging situations as they confront their own assumptions about teaching and learning, while also supporting PSTs who may be experiencing stressful placements in classrooms. In this article, we examine the learning undertaken by two teacher educators participating in a professional experience mentor program in a regional university in Australia. The research was conducted as a self-study in two phases. The first phase involved gathering data (email correspondence, mentor entry and exit surveys, meetings) and discussions throughout 2010; the second phase was a retrospective analysis of 10 critical emails. Identification and analysis of our assumptions revealed both the dominant categories of assumptions that underpinned our beliefs and practices, and the tensions and challenges we faced in our roles as mentors. Data analysis generated five themes that characterized our experiences as mentors: (1) ideals and reality; (2) emotions and assumptions; (3) transition to new leadership roles; (4) transitions as transformative experiences; and (5) tunnel vision. By systematically examining our practice, we developed a deeper understanding of the powerful ways that taken-for-granted assumptions influence our practice; we have also exposed the crucial influence of emotions and transitions on the growth of our professional identities. (Contains 2 tables.)