Based on a quasi-natural experiment of third-party environmental information disclosure policy,this study employs the Difference-in-Differences (DID) model to investigate the impact of informal environmental regulation policies on enterprise sewage discharge. The findings demonstrate that the third-party environmental information disclosure policy not only reduces corporate sewage discharge but also mitigates its intensity. A series of robustness tests confirm the reliability of these results. The third-party environmental information disclosure policy promotes a reduction in enterprise sewage discharge by enhancing public awareness of the environment and improving the government’s capacity for environmental governance. Heterogeneity analysis reveals that third-party environmental information disclosure has a more pronounced effect in reducing sewage discharge in cities with higher levels of economic development,industries with high water consumption,and state-owned enterprises. Urban digital economy development and green credit play crucial roles in augmenting the effectiveness of third-party environmental information disclosure policies in curbing sewage emissions. This article suggests intensifying efforts to disseminate environmental information while promoting digital economy growth and implementing top-level designs for green credit systems. By adopting an approach centered around informal environmental regulation,this paper presents a novel idea to promote emission reduction and pollution control among enterprises.