Student teachers are oftentimes encouraged to apply theoretical principles of social justice to their professional practice. However, this can be problematic when theoretical knowledge is contested or if it is inconsistent with the practices in their future workplaces. Studies in this area often examine student teachers' beliefs and understanding of their roles without taking account of how concrete working contexts shape what they see as possible in their practice. This study explored how students in two teacher education programmes based at the University of Edinburgh perceived their roles, practices and contexts for acting as agents of social justice. Mixed methods were used for data generation and triangulation including a questionnaire survey (n = 299) and scenario-based interviews (n = 9) to explore how students think about social justice issues in context. Student teachers generally saw agency for social justice as part of their role. Their understanding of the ways of addressing context-embedded issues of social justice focused on classroom practices while they raised concerns about how their practice depends on others in the system. We discuss the implications of these findings for teacher education.