This study examines how environmental norms embedded in foreign supply chain partners influence the green sustainability performance of Chinese domestic firms. We manually construct a novel Environmental Performance Index (EPI) based on the environmental standards of countries where foreign customers and suppliers are located. We find that firms with foreign supply chain partners from countries with stronger environmental performance demonstrate significantly higher levels of green sustainability. Further investigation reveals that the adoption of standardized green certifications, particularly ISO 14001, acts as a key transmission channel through which foreign environmental norms exert their influence. In addition, the effect of foreign environmental norms is contingent upon several factors, including international market exposure, domestic supply chain resilience, political connections, regional environmental regulations. Furthermore, we add new evidence to the dynamic supplier-customers relationship that concerning the transmitting foreign norms through supply chain, suppliers can play an active role in transmitting foreign environmental norms. These findings highlight the growing significance of sustainability standards in global supply chains as a catalyst for promoting environmentally responsible practices in emerging economies, offering valuable insights for both policymakers and corporations.