This article explores the dynamics of epistemic positioning and knowledge-building in classroom interaction in two postgraduate neuroscience classrooms. Using an interdisciplinary approach combining multimodal Conversation Analysis and Legitimation Code Theory (LCT), it examines how lecturers and students negotiate epistemic stance and status through interactional practices, and how these practices legitimise certain stances or “gazes” in relation to doing neuroscience. Drawing on six hours of video-recorded classroom interaction, the study uses detailed transcripts to uncover the epistemic positioning practices of two lecturers teaching modules on neurobiological bases of psychiatric disorders and addiction. The interactional data are reanalysed from the knowledge-building perspective of LCT, revealing that the two lecturers were operating different specialization codes and activating different gazes in terms of the social relations of both themselves and their students as knowers. The analyses demonstrate how slight shifts in interactional practices around epistemic positioning can have significant consequences for legitimating different knower positions in postgraduate neuroscience education. By combining micro-analysis with the sociological framework of LCT, the study offers insights into the complex dynamics of knowledge-building in advanced academic settings and offers tools for reflection on and enhancement of teaching practices in postgraduate science education contexts.