This study investigated the effectiveness of collaborative content representation (CoRe) design as a professional learning and development (PLD) intervention for enhancing practising science teachers’ pedagogical content knowledge (PCK) for teaching Year 10 (14-15-year olds) Electricity and Magnetism in New Zealand. There were three case study teachers in this study, each of whom were practising science teachers with a limited physics background. These teachers collaborated with six other experienced science teachers; three of whom also had a limited physics background, while the others were physics specialist teachers. All nine teachers were from the same school. PCK is a highly specific form of professional knowledge that teachers have, which enables them to teach particular content to a particular group of students. Since its inception, many approaches have been suggested for exploring science teachers’ PCK, but the exact nature of PCK and how to measure it has been problematic. To address these issues, two international PCK Summits have been held to advance the agenda of PCK research. The first Summit was in 2012, where a key output was a Consensus Model of PCK. The second Summit was in 2016, where researchers critiqued the use of that model, and discussed future PCK research. Outcomes of the second Summit are being published in the book Repositioning PCK in Teachers’ Professional Knowledge (due out in late 2018). This book introduces the Refined Consensus Model of PCK (RCM of PCK), which was used as conceptual framework to guide this study. Data was collected in three phases. In Phase One, case study teachers were interviewed about teaching Year 10 Electricity and Magnetism and then observed teaching this topic. Phase Two involved all participants in two CoRe design workshops, where they shared and debated ideas, and discussed pedagogical considerations with respect to teaching different concepts. The first workshop was a pilot exercise, while the second focused on Year 10 Electricity and Magnetism. All discussions were recorded and field notes were taken in workshops. In Phase Three, case study teachers were observed teaching the same topic to a different Year 10 class, then interviewed about changes to their practice. All participants were also asked about their overall experiences with collaborative CoRe design. Findings show collaborative CoRe design enhanced the case study teachers’ PCK for Year 10 Electricity and Magnetism. Development was seen in their subject matter knowledge, knowledge of instructional strategies, and knowledge of students’ understanding and learning. Furthermore, all participants saw value in CoRe design as it allows topics to be unpacked and teacher’s PCK to be shared. The teachers felt it was a worthwhile PLD intervention, they were interested in taking part in CoRe design in the future, and they offered suggestions to make it sustainable within their school. Thus, this study showed collaborative CoRe design is a worthwhile and effective PLD intervention for practising teachers. Not only did teachers explicitly identify their own PCK developments, enhancements were also seen in lesson observations. Schools could adopt this model of PLD to encourage collaboration amongst their staff and to allow for knowledge transfers between teachers with differing content backgrounds and pedagogical strengths.