The writing of narratives is a frequently used educational tool in teacher education. This activity has several aims, such as bridging the gap between theory and practice, transforming experience into knowledge, and fostering consciousness and reflexivity among prospective teachers. We consider that the writing of narratives, framed with some guidelines, represents a mean to build professional knowledge. To get a better insight into the processes involved in the writing of narratives, this article examines the cognitive and discursive mechanisms that underlie professional development. We rely on indicators of professional development observed through a psycholinguistic analysis of narrative texts. This type of text analysis is anchored in a Vygotskian perspective, according to which language; thinking and action are interdependent in the constitution of an individual's system of mental representations. In this article, we present an educational artifact for narrative writing, a grid for the analysis of discourses in the context of teacher education (the Analysis of Discourses About Professional Apprenticeship grid), our methodological framework and some results. The use of this grid is illustrated with examples of the prospective teachers' narratives and questionings. Finally, we suggest that professional knowledge results from the convergence between enunciative undertakings, regulations of action, and conceptions and reflective spectrum. This convergence determines the strength of professional knowledge built. Moreover, the texts that have been analyzed reveal the fundamental questionings the trainee teachers have when faced with the task of textualizing their professional knowledge as well as the meaning they give to their activity.