The purpose of this paper is to point out that sustainability reporting is also important for companies which are operating in developing countries, such as Serbia, but they have a lot of challenges on the road to sustainability reporting. The aim of the conducted research is to determine the level of sustainability reporting by the companies based in Serbia, to consider to which extent they are familiar with the sustainability reporting guidelines and to identify the application level of the Global Reporting Initiative (GRI) Guidelines in the preparation of sustainability reports. The research is realized by the method of descriptive statistics and correlation analysis. The results of the study show that the level of sustainability reporting by Serbian companies included in the sample is low and not satisfactory.