Citizens’ assemblies are relatively new political institutions that enable a randomly-selected group of everyday people to deliberate and make collective recommendations on climate policy and action. This raises significant questions about their legitimacy and the extent to which they resonate with the public and other societal actors. This research brief draws on evidence from climate assemblies and other participatory and deliberative processes, as well as targeted interviews, to evaluate what we already know about perceptions of legitimacy and resonance and the factors that are likely to shape these perceptions. Drawing on these findings, the brief considers what actions can be taken for assemblies to maximise their legitimacy and resonance.