The goal of this study was to evaluate the effects of the joint training activities of a cooperating teacher and a university supervisor during an advisory visit on (a) the professional development of a preservice teacher's activity and (b) the reorganization of mentoring activity following this visit. The results are considered from a theoretical perspective based on cultural-historical psychology (Leontiev, A. (1984). Activity, consciousness, personality. Moscow: Progress Editions.; Vygotsky, L. S. (1978). Interaction between learning and development. In: M. Cole, V. John-Steiner, S. Scribner & E. Souberman (Eds.), Mind in society (pp. 79–91). Cambridge: Harvard University Press.; Vygotsky, L. S. (1997). Thought and language. Paris: La Dispute.; Vygotsky, L. S. (2003). Consciousness, the unconscious, emotions. Paris: La Dispute.) and the clinical study of activity (Clot, Y. (2003). Vygotsky, consciousness as liaison. In: Vygotsky, consciousness, the unconscious, emotions. Paris: La Dispute, pp. 7–59.; Clot, Y. (2004). Work between functioning and development. Bulletin de Psychologie, 57(1), 5–12.; Clot, Y. (2008). Work and the power to act. Paris: PUF.; Clot, Y., & Faïta, D. (2000). Types and styles in work analysis. Concepts and methods. Travailler, 6, 7–43.). The discussion focuses on the conditions that led to the greater effectiveness of the advisory visit, which is an integral part of teacher training programs that alternate classroom work with co-analysis of the work. Proposals are also made for new directions in training supervisors and cooperating teachers with a view to building a training team.