This study focuses on how science teachers' Pedagogical content knowledge (PCK) can be captured and developed with the support of Content representation (CoRe) in combination with video-based reflection when they plan, teach, and reflect on their teaching in sustainable development (SD). The theoretical framework is based on PCK, and the Refined consensus model (RCM) is used as a theoretical lens for conceptualising links between teaching practice and PCK development. Eleven upper-secondary school science teachers participated in the study. Data from two teachers were chosen to illustrate representative examples from the analysis. The findings indicate that the use of CoRe and video-based reflection provides opportunities for teachers to make their knowledge of practice explicit and help them begin to identify aspects within their own practice that are important for the further development of teaching SD. The use of RCM as an analytical tool also makes an important contribution to how RCM can be used to identify and capture teachers' PCK.