This study reports on the trial of a school-based professional development process aimed at helping science teachers improve their inquiry-based science teaching skills. This process focuses on developing the pedagogical content knowledge of teachers through peer collaboration, under the guidance of a teacher educator. A multi-method interpretive approach is employed to capture the development of such knowledge in the research process. The findings reveal both the potential for collaborative professional development in in-service teacher training, and the challenges faced by both primary school science teachers and teacher educators in promoting inquiry-based science teaching. The implications of the findings are discussed to develop a more in-depth understanding of the nature and processes of pedagogical content knowledge. (Contains 1 table and 1 figure.)