This study investigates the impact of a mobile information environment on information asymmetry and investor sentiment among individual investors. To this end, we use a mobile stock trading ratio as a proxy for exposure in the mobile information environment and the Amihud (2002) daily illiquidity ratio, volatility, and difference in net buying dollar volume between individual and institutional investors to measure the degree of information asymmetry. This study also creates an investor sentiment index using the adjusted turnover rate, individual investors' buy–sell imbalance, and a relative strength index. We find that the mobile information environment significantly decreases individual information asymmetry and investor sentiment. Moreover, the effect in the KOSDAQ market, with high individual investor participation, is more significant than in the KOSPI. The results imply that individual investors may become gradually informed through information processing and cool down the over–heated investor sentiment in the mobile information environment.