Despite longstanding calls for social justice-oriented teaching, there remains limited understanding of how to achieve it. This paper reports findings from a research-development project that explored the experiences of UK-based primary science teacher educators participating in a nine-month equity-oriented professional development programme and offers insights for supporting teacher learning for social justice. Analysis of written reflections and open-ended interviews with 15 teacher educators identified three types of reflection that supported justice-oriented practice: personal privilege in relation to race, class, gender and science; the norms and values of educational professional development; and practical implementation of justice-orientated professional development with teachers and schools. We discuss the importance of creating safe and brave spaces for critical reflection for primary science teacher educators and highlight the productive potential of experiences of discomfort that generated humility, empathy and insights that resulted in more equitable practice. The paper underlines the value of supporting educators to embrace discomfort as part of social justice-orientated professional development and calls for a greater valuing of and support for expanded models of professional development that foreground critical reflection and go beyond 'top tips', 'quick fixes', and dominant norms around professional 'politeness'.