In the context of initial teacher training in French-speaking Belgium, this article focuses on traineeships, and more specifically on the construction of the evaluative judgment of supervisors during co-assessment. It aims to analyze the evaluative judgments produced by supervisors to see if they meet the characteristics of professional judgment in assessment, and more specifically the dimension of the situation that takes into account its singularity. This contribution aims to answer the following two questions: Does the evaluative judgment of the supervisor meet the characteristics of professional judgment in assessment? To what extent does the singularity of the situation influence this evaluative judgment? To answer these questions, we conducted an individual interview with eight supervisors from the same training institute. On the one hand, the analysis of the content highlighted the characteristics of the professional judgment implemented. On the other hand, it showed how the traineeship context has been taken into consideration during the construction of the evaluative judgment.