This paper examines the impact of Chinese local government hidden debt on corporate ESG greenwashing. Extending fraud theory, we reveal that hidden debt shifts the boundary between government and market that drives the factors behind ESG greenwashing. Using the ESG greenwashing indicator of listed firms in the A-share market and the hidden debt-to-GDP ratio of 31 provinces from 2012 to 2023, we find that local government hidden debt is positively correlated with corporate ESG greenwashing. The impact is more significant for firms that are state-owned, without active primary-level Party organizations, or not on China’s key pollution supervisory list. Mechanism analysis indicates that expansion of local government hidden debt brings firms with higher LGFVs’ share-holding for the SOEs, heavier environmental tax burden, and less social responsibility preference, all of which are related with ESG greenwashing. Reducing local government special debt and improving tax compliance can help alleviate this impact. These findings highlight the necessity of fiscal risk management in achieving genuinely sustainable corporate development.