In recent years, many local authorities in the UK have run local climate assemblies (LCAs) such as citizens’ assemblies or juries, with the goal of developing citizen-led solutions to the climate crisis. In this essay, we argue that a ‘convenient fiction’ often underpins the way local authority actors explain the rationale for running LCAs. This convenient fiction runs as follows: LCAs are commissioned as a response to the climate threat, and local decision-makers work through LCA recommendations to implement appropriate policies in their locality. We suggest that this narrative smooths over and presents as linear a process that is in fact messy and political. LCAs emerge as a result of political pressure and bargaining. Once LCAs have run their course, the extent to which their recommendations are implemented is dependent on power dynamics and institutional capacities. We argue that it is important to surface the messiness and political tensions that underpin the origins and aftermath of local climate assemblies. This achieves three things. First, it helps manage expectations about the impact LCAs are likely to have on the policy process. Second, it broadens understandings of how LCAs can contribute to change. Third, it provides a complex model that actors can use to understand how they can help deliver climate action through politics. We conclude that LCAs are important — if as yet unproven — new interventions in local climate politics, when assessed against this more complex picture.