Using data from Chinese A-share listed companies and their supply chain relationships from 2010 to 2022, this study examines the impact of environmental regulatory pressure faced by focal firms on the green transformation of their suppliers and explores the underlying mechanisms. The findings indicate that environmental regulatory pressure on focal firms significantly fosters the green transformation of suppliers. Mechanism analysis reveals that the environmental regulatory pressure on focal firms primarily drives the green transformation of suppliers through coordination in risk management, information transparency, and technological innovation. Heterogeneity analysis indicates that the greater the market concentration and supply chain influence of focal firms, the more significant the impact of environmental regulatory pressure on the green transformation of suppliers. Moreover, the financing constraints and environmental pollution levels of suppliers also exhibit notable heterogeneous characteristics. Further analysis reveals that the transmission of environmental regulatory pressure on focal firms between upstream and downstream firms in the supply chain is asymmetric, and that the transmission effect becomes more pronounced when focal firms hold a leading position in green development.