Second/foreign language (L2) education has largely concentrated on a macro-level approach to justice (i.e., social justice), while it has often neglected a micro-level viewpoint (i.e., classroom justice) rooted in organizational justice theory and social psychology, which considers the justice perceptions of educational stakeholders (e.g., students, teachers) within social environments (e.g., classroom). This chapter underscores the essentiality of classroom justice in L2 education. In this respect, we offer theoretical rationale and empirical evidence for incorporating classroom justice training into L2 teacher education, underscoring that the practice of justice in classroom is a pivotal characteristic of effective L2 teachers. Moreover, we delineate the core tenets of positive psychology (PP) and underscore the importance of L2 researchers’ investigating classroom justice as a positive psychological variable. We also emphasize the inherently interpersonal nature of L2 classrooms, requiring ongoing efforts to develop strong teacher-student connections and rapport. Following this, we explicate the substantial impact that classroom justice can have on fostering L2 student learning, particularly regarding students’ emotional and behavioral responses to course material and instructor. In conclusion, we advocate for the validity of classroom justice theory, research, and practice within L2 education, and stress the necessity of establishing a classroom justice framework supported by empirical findings from L2 instructional settings.