<p>Recent years have been marked by an upsurge in climate assemblies. These deliberative forums bring together randomly selected citizens to shape climate policy. Yet the rationales behind their introduction are not always well understood. The initial phase of these assemblies is likely to condition their influence on policymaking, in a context where participatory processes are often criticised for having little effect on policy. This paper addresses this gap by closely examining how a climate assembly was constructed in Belgium. Moving beyond official justifications, it explores the behind-the-scenes process through which its objectives were negotiated. The analysis shows that the assembly was shaped by an <i>ambiguous consensus</i>, a surface-level agreement among actors that left concrete objectives unclarified. It examines the causes and consequences of this ambiguity. In doing so, the paper calls for greater attention to the possibility that similar forms of ambiguous consensus may underpin other participatory processes, and to the risks such dynamics may entail. It also suggests that some climate assemblies may be guided by organisers’ expectations grounded in a depoliticised view of climate change and a narrow conception of public engagement. Overall, the paper offers a critical perspective on the transformative potential of climate assemblies.</p>