Right issue is one of the corporate actions that can affect the number and price of shares circulating in the market. The information content of the rights issue announcement is important because it will make the market react to the announcement. This study aimed to obtain empirical evidence regarding the existence of a market reaction to the announcement of the rights issue. The theory used in this research is Market Efficiency Theory. The approach used in this study is an event study. The observation period used in this study is 7 days by using a market-adjusted model in calculating abnormal returns. The population in this study were all go public companies listed on the Indonesia Stock Exchange and carrying out corporate actions in the form of rights issues during the observation period, namely 2018 – 2022. The sampling technique in this study was non-probability sampling using the purposive sampling method with a total sample of 128 companies. The data analysis technique used in this study is the one sample t-test analysis technique. The results of this study indicate that during the 7 days of observation, the market reacts to the rights issue. This proves that the announcement of the rights issue has information content that can influence investors in making investment decisions.