Recent research has begun to conceptualise the professional learning of practising teachers who take on leadership roles in schools. In this vein, this article draws on a qualitative interview-based study designed to investigate case writing as a professional learning approach. It focuses on the way in which writing of a published case encouraged teacher leaders to articulate their growing knowledge about leadership. Data indicate that teacher leaders anticipation of a public audience for their case writing was the feature that compelled them to consolidate and articulate their knowledge. But teachers traditional positioning as knowledge consumers (rather than as knowledge producers) led to their fragile confidence to later share the professional knowledge they had developed. The outcomes of this study hold implications for case writing as an approach to developing teacher leaders and for professional learning programs that seek to shift practitioner and public knowledge of teacher leadership into professional communities.