Purpose: The purpose of this research is to identify the combinations of factors leading to experience in sustainability reporting by Spanish public universities. Design/methodology/approach: Using a sample of 49 public universities in Spain, this paper identifies the combinations of factors on innovation profile, political and internal factors that explain the different degree of corporate social reporting experience with fuzzy-set qualitative comparative analysis. Findings: The study's findings are a contribution to existing literature as the results obtained point out three different configurations leading to this expertise, with a combination of different conditions based on innovation profile, political and internal factors. Also, the results reveal new characteristics of sustainable development strategies by universities, such as devoting a specific sustainability reporting section in the university website, creating a sustainability body in the university structure or submitting the sustainability report to external assurance. Research limitations/implications: This study refers only to Spanish public universities. In the future, new studies can enlarge the sample and analyse country effects and impact of public versus private status of universities on sustainability reporting strategies. Practical implications: The study's findings are important for university community, regulators and other stakeholders to start considering the need to somehow promote further sustainability reporting and assurance practices by universities, especially in a context of budget restrictions. Originality/value: This paper opens up a new line of research on sustainability experience using an innovative methodology (fuzzy-set qualitative comparative analysis) useful with small sample sizes, and provides a complete picture of sustainability reporting by Spanish public universities.