Citizens are central in any account of democracy. Any limitations on the capacity of citizens to exercise formative agency on complex matters of global justice can be overcome in inclusive deliberative settings. The citizen consultations conducted in the connection with the Sustainable Development Goals are assessed in this light. While pioneering, these consultations proved problematic in deliberative terms. We show how citizen deliberation could be promoted through transnational and global forums – most ambitiously, a Deliberative Global Citizens’ Assembly. We argue on both ethical and problem-solving grounds for the agency of the poor, currently often missing in global governance – though again the process for the Sustainable Development Goals tried to reach them more than did any previous global process. The agency of the poor can be promoted by poor-led social movements and institutional design to deliver on the need for the poor to act as a global community of interest. The poor from different parts of the world should deliberate together on what global justice requires on the ground, in contrast to national exercises that are limited in both democratic and epistemic terms.