Purpose: The purpose of this paper is to answer the following research question: What are the key factors of the participatory process for establishing sustainability reporting in German universities? Design/methodology/approach: To answer the research question, this study uses qualitative methodology, following the grounded theory approach and triangulation of qualitative methods for accessing data. Findings: The findings show that universities face a high level of difficulty in introducing sustainability reporting, which has an external and an internal dimension. Originality/value: This paper contributes to the understanding of sustainability reporting processes of universities from an internal perspective, specifically through experts who are involved in the preparation of sustainability reports. Furthermore, it delivers insights for a theory-based discussion, which may support universities in starting sustainability reporting activities and improving reporting processes.