The Aarhus Convention is a globally recognised benchmark for democratic environmental governance. However, no assessment exists on whether European MPAs comply with the legal standards set out by the Convention. Here, we focus on public authorities’ websites on MPAs as tools for promoting transparency, public involvement, and democratic processes. We assessed the websites of 61 European MPAs in thirteen countries using a survey structured by the three pillars of the Convention: access to information, participation in decision-making, and access to justice. We show that while most websites are used to disseminate information, they do not serve yet as participatory instruments. Very few have an area dedicated to public participation in decision-making and, when available, they provide scarce information on the outcomes of public involvement. Most websites provide general information on the MPA conservation objectives, but less than half provide access to reports on the results of management. Few websites provide information on available means to challenge unlawful acts. Websites’ potential as one of the most widely used, easily accessible, cost-effective sources of information and means for interaction with the general public should be better exploited. Increasing and facilitating the ability of the public to participate in MPA processes is key to ensure MPA success and environmental justice.