Teachers’ morally authentic action is an essential professional competence, but challenging to perform in real classroom situations. Although teachers are often aware of their external task demands and have also internalized their professional role requirements, it is often difficult for them to deal authentically in challenging moral situations in classrooms. Authenticity can be seen as a disposition to act on reasons and exercising in making decisions and constant deliberation. When practicing authenticity, teachers balance their thoughts and actions both with situational appropriate professional demands and personal preferences. This study explores ways teachers define and apply their moral authenticities during teaching. The study is based on qualitative data from student teachers’ practicum portfolios where they reported pedagogical dilemmas from their teaching practice. The analysis of qualitative case data (N = 110) revealed three different moral authenticities that were constructed from student teachers’ action reports: authenticity in moral appearance, authenticity in moral effect, and authenticity in moral commitment. The results emphasize the need to provide teachers with such competencies that help them to manage successfully and authentically in challenging moral situations. Implications for pre-service and in-service teacher education are also discussed.