Within the field of second language teacher education (SLTE), narrative has largely functioned as a vehicle for teacher inquiry, based on the assumption that such inquiry will ultimately bring about productive change in teachers and their teaching practices. Less attention has been paid to documenting what this change looks like or how engagement in narrative activities fosters teacher professional development. From a Vygotskian sociocultural theoretical perspective, we argue that the transformative power of narrative lies in its ability to ignite cognitive processes that can foster teacher professional development. We tease out the complex ways in which narrative functions as a mediational tool--narrative as externalization, verbalization, and systematic examination--in fostering teacher professional development, and we highlight the interplay between these functions by tracing teacher professional development in two teacher-authored narrative inquiries. We then turn to the centrality of narrative as a vehicle for teacher inquiry in transforming the field of SLTE itself. Specifically, we highlight various outlets, in both center and periphery contexts, where the products of teachers' narrative activities are functioning as a tool for knowledge-building and professional development practices that are working in consort to transform the professional landscape that constitutes the field of SLTE. (Contains 1 footnote.)