This paper examines whether—in the absence of mandated disclosure requirements—shareholder activism can elicit greater disclosure of firms’ exposure to climate change risks. We find that environmental shareholder activism increases the voluntary disclosure of climate change risks, especially if initiated by investors who are more powerful (institutional investors) or whose request has more legitimacy (long-term institutional investors). We also find that companies that voluntarily disclose climate change risks following environmental shareholder activism achieve a higher valuation, suggesting that investors value transparency with respect to climate change risks.