Faced with the increasing complexity of educational evaluation, teachers are increasingly requested to call upon their professional judgment. Such judgment is, however, rarely described in detail. This paper takes into account recent documents such as the Ontario College of Teachers’ standards of practice (2003a) and the competency framework of the ministère de l’Éducation du Québec (2001b) for the training of new teachers. It also examines the most recent literature on relevant questions dealing with the meaning of teacher’s professional judgment and builds a description of what it involves. Professional judgment is encountered in teaching standards of practice and in the interaction between the competency to evaluate and other components of the competence to teach as well as with teachers’ values and beliefs. Moreover, educational evaluation is considered not only as an object but also as a mean of developing professional judgment. To conclude, some essential characteristics are listed to help to circumscribe what is involved in professional judgment and what its impact may be in educational evaluation.