<em>This study employs the impact of warrant announcement on behaviour of stock prices on the Indonesia Stock Exchange (IDX). This study used the secondary data from the company that has issued the warrant on the Indonesia Stock Exchange in the period 2011 - 2018 with a population of fifteen companies. The sampling technique used in this study is purposive sampling the ten companies selected for the research sample. The method analysis used in this study is the event study technique using teen windows before and after listing date warrant. Hypothesis testing using t-test statistics. Before testing the hypothesis, all data is stationary test using the Dickey Fuller and Phillips Perron Test. The Result found that there are significant differences abnormal returns and cumulative abnormal return before and after the date of warrant listing on the Stock Exchange Indonesia, and the Indonesian capital market is semi strong form efficiency</em>