This paper explores the relational dynamics in 10 triads from one university-based teacher education programme in England. Positioning theory and frame analysis are integrated to understand how teacher educators, mentors, and student teachers make sense of the placement experience and distribute mutual rights and duties. Data were derived from observations of debriefs and in-depth interviews with all actors involved. Results reveal four different frames: the quality assurance frame, the school-university partnership frame, the socialisation frame, and the expert teacher frame, each opening up particular positions but also closing off others. This study challenges the uncritical acceptance of the benefits of triadic mentoring, while also offering a novel theoretical perspective for the study of its complexities.