Firms in China increase green innovation following a mandate that requires them to regularly disclose their corporate social responsibility (CSR) activities. Further analyses show that the CSR disclosure mandate leads to higher media coverage of disclosing firms' environmental issues, and the increase mainly comes from negative environmental news. By contrast, voluntary CSR disclosure does not affect corporate green innovation, and it increases positive but not negative environmental media coverage. These findings suggest that (1) it is the mandatory feature of the mandate, not the act of disclosure, that matters most for the positive effect on corporate green innovation; and (2) the negative media coverage induced by mandatory CSR disclosure plays a disciplinary role and promotes green innovation, while the positive media coverage induced by voluntary CSR disclosure does not.