Since the mid-1990s, the concept of professional learning communities has arisen in the education field in the West, aiming to improve teachers' professional competency by using collaborative approaches. Western studies indicate that these strategies help teachers achieve professional growth. Schools in China have had a long history of enhancing the professional competency of teachers by using collaboration in school-based contexts. But do professional learning communities in Chinese schools, especially in times of change, do the same for Chinese teachers? This study provides empirical data from Chinese teachers to assist global discussions on school-based professional development. The study uses qualitative data collection methods, including semi-structured interviews, observations and documentary analysis, to investigate how teachers from two subject departments in a secondary school in Shanghai enhance their knowledge and practice within their subject-based professional learning communities. Results show that members of these two communities have shared common goals and have developed a sense of collective accountability. The study also found that socio-cultural factors, such as the collectivist values, authoritarian-oriented practices and influences of interpersonal relationship, are crucial in the development of Chinese professional learning communities, even though different communities may differ in other respects. (Contains 1 table and 1 figure.)