This study focuses on two preservice teachers who experienced significantly different mentoring relationships in their two placements during a one-year teaching degree in a university in Western Australia. Data were collected through three rounds of semi-structured interviews, reflective journals and classroom observations. The findings indicated that mentor teachers' mentoring styles considerably informed the preservice teachers' perceptions of themselves as teachers and facilitated or inhibited their professional development. Implications for practice include teacher education programs invest more time and rigour in selecting and preparing mentors for their crucial role.