<p>Building on the quasi-natural experiment created by the implementation of SEC and CSRD disclosure rules, we employ a PSM-DID model to analyze changes in carbon emissions among Chinese suppliers with significant U.S. and EU clients. Our findings reveal that carbon emissions among these Chinese suppliers significantly decreased following the introduction of disclosure policies by the U.S. and EU. Mechanism analysis suggests that the carbon emissions reduction effect is primarily driven by four key mechanisms: stakeholder carbon focus, firm environmental investments, government green subsidies, and external strategic collaboration. Heterogeneity analysis at supply chain level reveals that the effect is greater among suppliers with high supply chain dependency, low resilience, and supply chain closure. Heterogeneity analysis at industry level reveals that the effect is stronger among suppliers operating in industries with higher competition, greater technological intensity, and tighter vertical integration. Heterogeneity analysis at firm level reveals that the effect is more pronounced among privately owned firms, high-export-intensity firms, and those with supply chain equity connections. Additional analysis reveals that the emission reducing effect is most pronounced when suppliers serve both U.S. and EU clients, suggesting compounded regulatory pressure from dual exposure.</p>