In recent years, an increasing number of scholars and politicians have called for institutionalising deliberative citizen participation within Parliaments. The Parliament of the German-speaking Community of Belgium has paved the way in this direction by institutionalising a permanent deliberative citizen assembly that is directly linked to the parliamentary process. It consists in a permanent Citizens’ Council drawn by lot, which can initiate Citizens’ Assemblies, also drawn by lot, whose mission is to deliberate and formulate recommendations on the subject that the Citizens’ Council had submitted to them. At the end of the deliberations, the recommendations are discussed in a joint committee between the members of the Citizens’ Assembly, elected representatives and the minister in charge. The latter two then need to indicate whether and how the recommendations will be implemented by parliamentary or governmental measures—with rejections requiring specific justification. This article analyses how such a far-reaching process of citizen participation and deliberation became introduced at the core of the parliamentary institution and what are its features.