In the practice of teacher education, most would agree that critical reflection in and on the process of learning to teach and the activities of teaching play a central role in teachers' professional development. Using Vygotskian sociocultural theory, we examine how narrative inquiry functions as a culturally developed tool that mediates teachers' professional development. We analyzed narratives written by three teachers of English as a second/foreign language set in three different instructional contexts. Our analysis suggests an interwoven connection between emotion and cognition, which drove these teachers to search for mediational tools to help them externalize their experiences. The activity of engaging in narrative inquiry created a mediational space where teachers were able to draw upon various resources, such as private journals, peers and "expert" or theoretical knowledge, that allow them to reconceptualize and reinternalize new understandings of themselves as teachers and their teaching activities. The intersection of experiential and "expert" knowledge provided a discourse through which these teachers named experiences and constructed a basis upon which they grounded their transformed understandings of themselves as teachers and their teaching. Depending on where these teachers were in their professional development when they wrote their narratives, we uncovered evidence of idealized conceptions of teaching with commitment to action as well as the transformation of teachers' material activities. Implications for the role teachers' narrative inquiry may play in teacher education programs are provided.