The Green Deal (GD) and the Conference on the Future of Europe (CoFoE) are both central to the EU's environmental, economic and social sustainability, even as many questions persist regarding their processes and outcomes. This article considers both processes as essential catalysts for, and tools of, a more polycentric Europe. It specifically wants to harness the problem-definition and problem-solving abilities of such a polycentric system through greater participation, solidarity and trust. By ensuring citizen empowerment through citizen assemblies such as the CoFoE, the success and legitimacy of the GD, as a central part of the EU's sustainability agenda, could be strongly amplified. This article highlights several procedural and substantive overlaps and synergies that present low-cost, high-gain opportunities to make these processes mutually reinforcing. More generally, the CoFoE, and possible future iterations, should be central to the EU's democratic integration and its longevity.