Despite the increasing attention that the circular economy (CE) has received at the international level in recent years, the literature has paid limited attention to the importance of institutional factors that may influence firms’ disclosure of CE. Thus, there is a gap in the study of CE disclosure, especially when compared with other studies dedicated to environmental disclosure. This paper aims to fill this gap by investigating the institutional pressures, in terms of coercive, normative, and mimetic factors, that influence firms’ behavior with respect to CE disclosure. This research focuses on a sample of 366 nonfinancial firms, operating in 14 EU countries between 2015 and 2020. The results show that coercive and mimetic institutional pressures positively influence the level of CE disclosure issued by the firms. More specifically, the stringency of the environmental policy (coercive pressure) and the belonging to an environmentally sensitive sector (mimetic pressure) have a positive impact on the CE disclosure provided. With respect to normative pressure, the results are mixed. In fact, only the adoption of Global Reporting Initiatives’ (GRIs) standard requirements is positively and significantly related to CE disclosure. The presence of an external assurance, as well as the commitment to the SDGs, is not significantly related to the CE disclosure. The absence of an analytical standard that organically addresses the issue of CE, by guiding companies in their disclosure, may explain the irrelevance of these factors in the process of convergence of the information produced. This research contributes to this area by filling a gap in the CE literature, providing some insights into the determinants of disclosure and the role of institutional pressures in influencing the level of CE information. In addition, the research adds to previous studies on disclosure by measuring the CE information provided by companies with an indicator developed based on specific environmental items collected from the Refinitiv Eikon database, which could be used in future research. The findings of this paper have some important practical implications. In particular, the results confirm to policymakers that stricter regulations have a positive impact on disclosures related to the CE. Thus, a new specific European regulation should promote more homogeneous and analytical CE disclosure, increasing the sensitivity among firms and practitioners on this topic. A similar approach may be followed for the same purpose by other regional or local policymakers. The paper also emphasizes the necessity of introducing more stringent regulations on assurance and SDGs by the regulatory or professional bodies to achieve greater uniformity of behavior by firms.