The effects of macroeconomic announcements on the stock market have been examined by various researchers. It is noteworthy that studies examining the effects of macroeconomic announcements on the stock market in Turkey, which is one of the developing countries, are quite limited. Therefore, it is thought that this study will contribute to the literature in terms of examining the possible impact of economic growth announcements, that is one of the macroeconomic announcements, on the construction sector index in Turkey. In this study, it is aimed to examine whether the economic growth figures in Turkey when announced to the public affects the Turkish Construction Sector index returns, and whether the Turkish Construction Sector is effective in semi-strong form. Unlike other studies, Efficient Markets Hypothesis was used and event study method was employed in this study and using Efficient Markets Hypothesis and employing of the event study method is thought to be another contribution of the study to the literature. In this context, the period between the 4th quarter of 2012 and the 4th quarter of 2021 is discussed and the market model is determined as the estimation model of the research. The event window interval (t-5, t+5) is opened as 11 working days, and the estimation window interval (t-20, t-6) is opened as 15 working days. According to the findings, it is concluded that when the economic growth figures in Turkey are announced to the public, the Turkish Construction Sector reacts to these data quickly, fully and accurately, and therefore the index created by the Turkish Construction sector (BIST Construction) is effective in semi-strong form. It is important for both individual and institutional investors that the construction sector operates in a semi-strong form. It has been evaluated that it is not possible for investors to obtain abnormal returns in the relevant sector index by taking advantage of the publicly announced economic growth announcements.