This research describes the relation between the professionalism and the cognitive dissonance that exists in the Greek teacher. Basic axis of this research is the theory of cognitive dissonance, as it was put forward by Leon Festinger. The sample consists of 720 teachers from all over Greece. In the results of the research it is included the fact that there is cognitive dissonance in some cases mainly due to his/her absence from his/her family because of educational reasons and seminars. Also, some differentiations were observed as far as the sexes are concerned, with the women facing greater cognitive dissonance than their men colleagues.