This analysis looks into the complex relationship between two trends in international governance: an increase in multilateral arrangements between countries in order to govern internationally on the one hand, and a lack of democratic control over the decisions taken by multilateral organisations or conferences on the other. Multilateralism in the modern sense refers to an international mode of operation involving peaceful negotiations and diplomacy, also referred to as a ‘rules-based international order’ or ‘rules-based multilateralism’. Several European countries have recently launched initiatives in support of multilateralism, in reaction to the increasingly unilateral behaviour of states undermining the existing rules-based international order. Apart from the European Union, no other multilateral organisation has a parliamentary body with the competence to block or amend its decisions, which indicates that there is a democratic deficit in these multilateral organisations. An initial response to such a democratic deficit is the involvement of national parliaments in international decision-making. This is known as ‘parliamentary diplomacy’. Secondly, the involvement of civil society in international decision-making through protests, petitions, consultations or participation can also enhance democracy. Thirdly, the organisation of national referenda on international decisions can be used by national governments or citizens’ initiatives to increase democratic legitimacy. Fourthly, a lack of democracy at international level can also be countered by creating an ‘alliance of democracies’, aimed at multilateral cooperation between democratic countries rather than the democratisation of multilateral organisations. These are mostly alliances of Western countries, which risks emphasising the differences between West and East or North and South. Three short case studies of parliamentary diplomacy with the strong involvement of the European Parliament (the Parliamentary Conference on the World Trade Organization (WTO), delegations to the Conferences of Parties of climate change agreements and the NATO Parliamentary Assembly) show that enhancing multilateral democracy is not the only aim of parliamentary diplomacy and that each case reveals a different mix between the ‘parliamentary’ aspect of democratisation and the ‘diplomacy’ aspects of information exchange or influencing.