In the context of the increasingly emphasized green development concept, the prevalence of corporate greenwashing has emerged as a pressing issue. This study selects A-share listed companies from 2012 to 2023 as its research sample. By adopting text analysis to parse the field research minutes of institutional investors, it measures the communication effectiveness between them and the companies. Subsequently, a benchmark regression model is established to explore the relationship. The empirical results suggest that communication from institutional investors can significantly curb corporate greenwashing. However, competitive pressure acts as a negative moderator, reducing the inhibitory impact of such communication. The heterogeneity analysis further reveals that this inhibitory effect varies across different scenarios. It is more evident in non-heavy-polluting enterprises, under strict environmental regulations, and when the number of investigations is relatively small. This research enriches the theoretical understanding of corporate greenwashing by exploring the relationships among various influencing factors. It also broadens the measurement scope of institutional investor communication. Practically, the findings can guide enterprises towards green development, safeguard investors’ interests, and stabilize the market.