This study examines the effect of retail investor-firm communications (RIFC) on corporate ESG performance. Exploiting the unique setting of Chinese investor interactive platforms which enable retail investors to pose questions and require firm answers, we show that RIFC significantly improves corporate ESG performance. The consistent evidence is obtained by employing the difference-indifference estimation, Oster’s test and alternative indictors, strengthening our confidence in the causal link between RIFC and corporate ESG performance. Furthermore, we identify two potential economic channels underlying our results: strengthening monitoring pressure and alleviating financial constraints. Our finding further reveals that RIFC drives genuine improvements in ESG performance rather than greenwashing practices. Collectively, this study advances our understanding of the interplay between retail investors and corporate ESG performance, providing a stepping stone toward effective solutions to corporate sustainable development.