The study aimed to determine the extent to which sustainability issues are disclosed by banks operating in Slovakia and Turkey between 2019 and 2021 and whether there is a significant difference in the level of information disclosed within the scope of sustainability between countries and years. To determine the level of disclosure of sustainability information, firstly, content analysis was conducted within the scope of GRI4. Then, a two-way ANOVA test was applied to determine the statistical differences between countries and years in terms of the level of information disclosure. According to the results of the study, the highest level of disclosure for banks in Slovakia and Turkey was for general standards information, while the lowest level of disclosure was for environmental information. In addition, significant differences were determined in terms of reporting across both years and countries. The disclosure score for countries has shown a steady but small increase over the years. In addition, the information disclosure scores of the countries were close to each other, especially for 2019 and 2020, and there were no major differences. This research contributes to the literature by comparatively presenting the level of sustainability reporting of large-scale commercial banks in the banking sector of two countries within the scope of the GRI Financial Services Sector disclosure index.