This article examines the role of European think tanks in public diplomacy efforts of the EU. It builds on Bourdieu’s field theory and concept of capital using data from EU official documents, website materials, and semi-structured interviews with representatives of think tanks from Brussels, France, Slovenia, and the United Kingdom, as well as their networks and the EU institutions. The article argues that EU institutions provide financial support for think tanks to obtain political capital in the form of internal and external legitimacy. The European Commission mobilises think tank academic capital by funding their educational activities, which helps to deal with the “democratic deficit” and plays the role of intellectual “soft power” by training current and future policymakers in Europe and beyond as potential allies in competition with other regions. Due to the particularity of the EU public sphere, characterised by the lack of outreach mass media, the European Commission tries to improve its capacity to shape public opinion at the European and global levels by using think tank publicity capital in its communication activities via new media platforms, distinguished by direct access to wider audiences. The European Commission benefits from think tank social capital, encouraging them to create transnational networks regarded as contributing to the promotion of integration within the EU, building relations with candidate countries, and strengthening its position in multilateral negotiations. Although the citizen’s dimension is not always at the core of practices of European think tanks, this article demonstrates their effectiveness as a channel of public diplomacy towards transnational publics.