The originality of our work consists in analyzing the process of identity construction of two beginning university teachers (EUD) in the region of Tunis from a cross-case study. The observation in situ of four theoretical courses, the semi-directed interviews (a priori, ante session, post session and post-coup) and the analysis of contents allowed us to clarify the mechanisms (conscious and unconscious) of construction of the identity process of the EUD and the evolutionary and upsetting dynamics of this identity construction (and professional) in the phase of the entry in the profession. We have highlighted the impact of the relationship to knowledge on the construction of the professional identity of EUDs and the professional development of these teachers. The EUD's desire to teach seems to be correlated with the student's desire to learn, which, according to our research results, is above all a projection of his or her teacher and a source of identification and recognition for the student.