<p>Biodiversity loss has emerged as a critical global sustainability challenge, yet corporate biodiversity disclosure remains limited and uneven. This study examines whether government-led environmental policies can enhance ecological transparency by analyzing the impact of China’s Zero-Waste City policy on corporate biodiversity disclosure. Using panel data of Chinese A-share listed companies from 2010 to 2022 and a difference-in-differences framework, we find that the policy significantly increases firms’ biodiversity disclosure. Mechanism analyses indicate that the effect operates through strengthened regulatory pressure, market-based incentives, and social supervision. Heterogeneity tests reveal stronger responses among state-owned enterprises, non-polluting firms, and technology-intensive industries, suggesting that governance alignment, resource capacity, and reputational incentives condition policy effectiveness. These findings remain robust across multiple specifications and placebo tests. This study contributes to the literature by providing evidence that urban sustainability policies are associated with changes in firm-level biodiversity disclosure beyond their immediate regulatory scope. The results also provide policy implications for integrating biodiversity considerations into corporate sustainability reporting and for designing governance frameworks that promote ecological accountability.</p>