While there has been a rise in the demand of learning Mandarin in the United Kingdom in the last decade, the development of teaching Mandarin as a foreign language is still at its initial stage. In particular, research shows that there is inadequate continuous professional learning opportunities for in-service Mandarin teachers. Furthermore, as many of the Mandarin teachers are native-speakers without formal training prior to taking up their posts, they might not have the relevant Mandarin-specific pedagogical knowledge. This study aims to explore the impact of professional learning for Mandarin teachers using an intervention approach. Participants (N=50) will attend a whole day workshop on the teaching of Chinese characters. The workshop will be conducted in England and Scotland. Focusing on understanding teacher efficacy and possible changes of their pedagogical approaches, the data will be collected by administering surveys before and after the workshops and conducting semi-structured interviews of the teachers after the workshop as well as the artefacts developed by these teachers during the workshop. The design of the study was guided by Gregoire’s (2003) cognitive-affective model of conceptual change (CAMCC), which teacher efficacy plays a key role in mediating teachers’ conceptual change by the enhancement of subject knowledge. It is hoped that the findings can reveal the professional learning needs of in-service Mandarin teachers and provide insights into the different ways of improving in-service Mandarin teachers’ efficacy as well as their knowledge and skills of teaching Chinese characters in the classroom