T This research aims to determine the differences in abnormal returns and stock trading volume activity before and after the announcement of the elected president and vice president by the KPU in 2024. This research uses secondary data from companies listed on the IDX. The sampling technique is a saturated sample, that is, the sample uses all members of the population of 924 issuers. The data analysis technique for this research uses event study using SPSS to test differences in abnormal returns and trading volume activity before and after the announcement of the president and vice president elected by the KPU. The results of this research show that, firstly, there is a difference in abnormal returns before and after the announcement of the elected president and vice president by the KPU in 2024; secondly, there is no difference in trading volume activity before and after the announcement of the elected president and vice president by the KPU in 2024. This research provides valuable insight into how major political events, such as the announcement of the elected president and vice president, can influence the stock market, which can be used by various parties to make more informed and strategic decisions. The results of this study support the semi-strong form of market efficiency theory, where major public information such as significant political announcements is immediately reflected in stock prices, indicating that markets are quite efficient in processing and responding to new information.