Corporations increasingly define their corporate social responsibility (CSR) activities as a part of their business. However, is this trend beneficial to investors? Based on an event study methodology and a sample of Chinese listed companies, we extend the literature on voluntary disclosure by exploring the role of CSR disclosure in reducing stock market information asymmetry, as proxied by share price volatility and liquidity. Our results show that the share price volatility after CSR disclosure is lower than before CSR disclosure; however, the trend is that it decreases first and then increases for three months following disclosure. Stock liquidity also significantly improves after CSR disclosure; however, it increases first and then decreases. Additionally, by dividing CSR disclosure into economic (hard) disclosure and generic (soft) disclosure, we find that the reduction in information asymmetry is higher for hard disclosure than soft disclosure, suggesting that although CSR disclosure does indeed have an impact on investors’ behaviour in China, an economic‐based disclosure contributes more substantially. Finally, to better understand the characteristics of the Chinese financial market, we also explore the role of marketisation with results that show that the effect in reducing information asymmetry is greater for companies located in a region with a higher degree of marketisation.