The issue of social justice has been regularly addressed in many published papers in mathematics education research, particularly after 2000, when the discipline took a more explicit socio-political turn. However, there does not appear to be a consensus as to what the term designates and includes. This paper is a systematic review of the empirical studies published from 2000 until the middle of 2019 that explicitly address social justice from the perspective of practising mathematics teachers and/or teaching. More specifically, we examine (a) how social justice is conceptualised in the identified studies, (b) what specific issues are investigated and methodological approaches employed to do so, and (c) the main key points that arise from their empirical findings. Implications and suggestions of how the field can move forward are discussed at the end.