Environmental information disclosure (EID) is an important measure to promote multiple subjects’ collaborative management of pollution emissions. In this paper, we first measure the carbon dioxide (CO₂) emissions of 282 cities in China from 2006 to 2020, and clarify the theoretical mechanisms and transmission channels of EID affecting CO₂. Subsequently, the Time-varying difference-in-differences (DID) and the mediation effect model are used to assess the impact of EID on CO₂ and its transmission mechanism, respectively. The study shows that although EID is a voluntary environmental regulation, the policy significantly reduces CO₂, and this reduction effect has regional and low-carbon policy intensity heterogeneity. The study also shows that green technology innovation and energy intensity mediate the carbon reduction effect of EID. This study has important reference significance for reducing greenhouse gas emissions and improving the quality of economic development.