Teachers are one of the professional classes most vulnerable to emotional instability and fatigue associated with their professional activity. The present study is a systematic review about burnout in Portuguese teachers and has two main objectives. The first is to understand the state of the art of the burnout phenomenon in Portuguese teachers from basic education to secondary education. The second is to analyze the types of variables considered in the exploration and understanding of the burnout phenomenon, from a three-dimensional structure: personal, organizational, and classroom. Results show that the set of personal and organizational variables are the most frequently analyzed in studies on burnout in teachers. Nevertheless, the results of the analyzed studies are unclear and inconsistent, highlighting the need for further studies that allow to clarify the role of different variables on burnout in Portuguese teachers. More studies are needed to determine the actual extent of burnout and, consequently, to design educational and psychological interventions to support teachers.