Background/purpose: The significant role of mentor teachers during practicum studies necessitates training that specifically addresses mentoring expectations in the teaching context. Drawing on critical constructivist teacher education, this study aims to investigate the expectations of student teachers, mentor teachers, and university supervisors from mentoring. Materials/methods: Data were collected from 79 preservice teachers, 37 mentor teachers, and six university supervisors through a researcher-designed questionnaire and in-depth, semi-structured interviews. Results: Analysis of the participants' responses showed that all three groups chose giving feedback to student teachers and knowledge on mentoring duty as the two most important themes that mentor teachers should receive training for. In addition, observing student teachers was another prominent theme for the mentor teachers group, whereas the student teachers group underlined the theme of knowledge on practicum procedures as a concern to be addressed in the training of mentors. Conclusion: The results provided not only valuable data to inform an online mentor training program, but also uncovered concerns experienced by all three participant groups, highlighting certain actions that are recommended to be taken.