Purpose: This study aims to answer the research question: How to evaluate the structure of global university sustainability rankings according to the Berlin Principles (BP) framework. Design/methodology/approach: The authors investigated two global sustainability rankings in universities, The UI green metric World University Ranking (WUR) and the Times Higher Education World University Rankings (THE-WUR). The authors performed content analysis regarding their evaluation criteria and assessed both rankings using the BP framework. Findings: Results show that there is still a gap to be filled regarding the specificity of global university sustainability rankings. Although the THE-WUR had a better performance in this research, there are several items for improvement, especially regarding the methodological procedures. There are structural differences, limitations and points for improvement in both rankings. Besides, it may not be possible to have a unique and more appropriate ranking, but one that can be more suitable for a contextual reality. Practical implications: This study can be helpful for university managers when deliberating on the most appropriate ranking for their institutions and better preparing their higher education institutions for participating in sustainability-related rankings. Besides, it suggests possible improvements on the rankings' criteria. Social implications: The authors shed light on challenges for improving the existing university sustainability rankings, besides generating insights for developing new ones. In a provocative but constructive perspective, the authors question their bases and understandings of being "the best university" regarding sustainability. Originality/value: This is the first study that provides an in-depth analysis and comparison between two of the most important global university sustainability rankings.