This study explores the connection between corporate governance and sustainability performance through the mediating role of corporate governance and the moderating role of top management environmental concern, taking into account the perspectives of agency theory and stakeholder theory. Data were collected through a questionnaire survey of 314 employees working in SMEs operating in China, and the data analysis was carried out using Smart PLS 4 and SPSS. The results indicate that green corporate governance and green finance have a significant impact on corporate social responsibility, which in turn positively affects sustainable performance. Corporate social responsibility significantly mediates the link between green corporate governance and sustainable performance. Meanwhile, corporate social responsibility also mediates the relationship between green finance and sustainable performance. Additionally, top management environmental concern moderates the relationship between corporate governance and sustainable performance significantly, strengthening the impact of corporate social responsibility on sustainable performance. The study contributes to the literature by exploring the relationship between corporate governance, green finance, and sustainable performance in the context of Chinese SMEs. The study’s findings have significant implications for policymakers and managers interested in promoting sustainable development.