The purpose of this study was to improve the pedagogical content knowledge (PCK) of pre-service chemistry teachers using a school experience course enriched with PCK development tools such as CoRe as a lesson planning form, observations of mentor teachers’ teaching by using an observation form prepared based on PCK components, discussion sessions on these observations, and reflections on their teaching. Some valuable results of the study indicated that pre-service teachers' science teaching orientations did not change during the study. However, all participants' knowledge of learners and knowledge of instructional strategies improved by the end of the study. Knowledge of curriculum and knowledge of assessment are the components of PCK in which some pre-service teachers showed no improvement.