This study was designed primarily to investigate the impact of school-based curriculum development teams on teacher development within the tradition of school-based curriculum development. The results are expected to provide valuable insights for teachers, school management and policy making. Teacher interviews in a primary school in Hong Kong were conducted to evaluate the extent to which teacher engagement in curriculum decision-making processes, which are within two school-based curriculum development teams, led to teacher professional development; these were triangulated with video-taped meetings and tryout lessons. Qualitative evidence showed that participating teachers have each undergone professional development through the processes involved in the planning, experimenting and reflecting (PER) model, which is also upon curriculum practice and innovation under certain conditions. However, the complex structures and processes that have been established to involve teachers in curriculum decision making need further empirical and theoretical work. While previous papers on the studies focused on teacher development and pupil learning, this paper, based on interview data, aims to focus on the functions of distributed leadership, and how the leadership styles of consultants and panel heads mediate the interactional patterns and therefore the discourses in the Mathematics and Chinese development teams in the second action cycle of the innovation project. (Contains 2 tables and 1 figure.)