AbstractIn the context of increasing attention on museum sustainability, this research adopts a dictionary‐based, content‐analysis approach to measure the degree of sustainability disclosed in European museum annual reports and similar documents. The analysis is carried out through the lens of institutional theory, assuming that the presence of formal and informal regulations positively affects the level of sustainability in annual reporting practices. Furthermore, the paper discusses the level of sustainability disclosed by different types of museums and the impact of the COVID‐19 pandemic on the extent of sustainability‐oriented reporting. The article compares top public museums in the UK and France, the European countries where accountability practices are most deeply rooted for legal and cultural reasons, and where the most visited museums in the world are located. The findings show that the type of museum and the country significantly affect the ESG (Environmental, Social, and Governance) score, whereas mentioning COVID‐19 or the year of publication does not.