Our scholarship grounded in a Vygotskian Sociocultural Theory (VSCT) stance and that of other VSCT-informed teacher educators/researchers not only employs VSCT as a theoretical lens to understand the development of L2 teacher/teaching expertise but intentionally deploys specific principles and concepts of the theory in/through systematically organised language teacher education (LTE) practices to promote it. This scholarship therefore embraces a dialectical unity of theory and practice – praxis – in which theory guides practice while practice shapes theory. We devote this chapter to VSCT-informed scholarship that originates in a dialectical approach to theory/practice in the specific social activities of LTE that take place in a myriad of sociocultural, historical, political, economic, and institutional contexts. We overview key principles and concepts of VSCT to show how VSCT could be used to inform the practices and interactions of LTE programs in systematic ways. We then highlight recent VSCT-informed LTE scholarship that illustrates the practices and interactions in which teacher educators have challenged teachers’ everyday concepts, developed teachers’ conceptual thinking, and promoted teachers’ enacting conceptual teaching.