The present study aims to understand, through the analisys of mediation of the speech therapist, the process of the coconstruction and re(con)textualization of the narrative of a deaf teenager in a workshop called Oficina Fonoaudiológica de Língua Escrita Mediada pela Libras, in the Ambulatório de Surdez of UFRJ. This research has a qualitative and interpretative nature, through a case study, with theoretical and methodological focus in the Linguistics of Professions. The analitycal categories were established from the Conversational Analysis in institutional context, from the Conversational Narrative and its re(con)textualization, and from the Interactional Sociolinguistics. Data generation was done with video recording. For transcription, interaction conventions, as well as studies on Brazilian Sign Language, were used. The analysis indicates that the mediation was fundamental for the development of the interactional process of coconstruction of the narrative and its re(con)textualization, from Brazilian Sign Language to written Portuguese. In her participation, the speech therapist used questions, reformulations, repetitions, evaluations and explanations, and tried to coconstruct the narrative in signs, besides evoking reflection on the written narrative speech. The teenager has an active participation in the interaction, but she needs the mediation concerning the narrative elements, throughout the process, which involves the stages of telling, writing and rewriting. This study contributes to the reflection on the interactional order of the speech therapist professional practice aiming at the deaf s autonomy in the development of her narrative discourse in Brazilian Sign Language and written portuguese, which is still relative in the institutional context.