This study examines the relationship between firms' environmental, social, and governance (ESG) performance and the linguistic tone of ESG reports to assess whether such communication serves either as a genuine signal of sustainability commitment or a symbolic tool for legitimacy seeking and impression management. Using a panel dataset of Chinese A-share listed firms from 2007 to 2022, the study analyzes how companies strategically employ narrative tone within an institutional environment characterized by strong conformity pressures and weak validation mechanisms. It advances the corporate social responsibility decoupling literature by empirically addressing the symbolic-substantive gap in corporate disclosure and highlighting internal organizational factors that affect greenwashing practices. Finally, it offers insights into strengthening the credibility and transparency of ESG reporting.