Enhancing the performance of corporate green supply chain management (GSCM) represents a critical enabler for delivering on the central imperatives of the global low-carbon transition. Using panel data of Chinese listed companies from 2003 to 2022, this study employs a staggered difference-in-differences (DID) approach to examine the impact of the Low-Carbon City Pilot (LCCP) policy on firms' GSCM performance. The results show that the LCCP policy significantly improves firms' GSCM performance, and this effect remains robust across a range of sensitivity tests. Mechanism analyses reveal that the policy operates primarily by stimulating green innovation and increasing investment in environmental protection equipment. Furthermore, financial constraints play a significant moderating role: the positive effect of the policy on GSCM performance is stronger when firms face fewer financing constraints. Heterogeneity analysis indicates that the policy effects are more pronounced among non-heavy-polluting enterprises, those located in resource-dependent cities, and ISO 14001-certified enterprises. This study provides novel micro-level evidence on the environmental governance effects of place-based climate policies, and offers key policy implications for scaling up low-carbon city pilots and promoting corporate supply chain decarbonization.