Teacher leadership plays a critical role of school improvement. However, the leadership development of beginning teachers is often neglected. This presentation examines the impacts of principal-teacher interactions on the teacher leadership development of twenty beginning teachers in Hong Kong. Case study approach was adopted. Data were collected through semi-structured interviews and documentary evidence such as school development plans and school reports. Results show that the beginning teachers were able to take up formal and informal roles of teacher leadership early in their teaching career. The characteristics of the principal practice and three types of impacts of principal-teacher interactions on developing teacher leadership are identified. This presentation highlights the role of principal in teacher’s leadership development. Implications for school leadership and teacher education programmes are also discussed.