The concept of sustainability is continuously used in the environment, tourism, architecture, businesses and economy. In this study, the sustainability reports of public companies listed in BIST Sustainability Index are analysed under economic, environment and social categories identified by in the Global Reporting Initiative Reporting Guide. The aim of the study is to determine the disclosure practices of listed companies about sustainability issues. The sustainability reports of companies listed in BIST Sustainability Index are analysed with content analysis using Nvivo software programme and the result of the analysis are evaluated. The results of the study indicated that the most highlighted issues are as follows; in economic sustainability economic performance, in environmental sustainability products and services, in social sustainability employee and, health and safety issues. Further, the results of the regression analysis indicate that as the firm age and number of employees increase firms issue more comprehensive sustainability reports.