This study examines the semiotic mechanisms that facilitate the construction of professional teacher identity during a collaborative learning activity for pre-service teachers. From a historical and cultural perspective, semiotic mechanisms are forms of action that allow the creation and transformation of ideas shared between individuals. The study applied content analysis and sociocultural discourse analysis to a work session between student teachers. Two main mechanisms were identified: 'conquering silence' and 'constructive identity reformulation'. The first allows the individual to keep a conversation going and to position themselves as a teacher during moments of silence. For the second, the individual adopts the perspective of a teacher to summarise interventions made by the group. The results show how these mechanisms facilitate the production of teacher-voiced positions, contributing to the development of professional identity. These findings underline the importance of peer interactions in the construction of professional identity and have implications for the design of training activities.