How climate change is framed within CAs is critical for both the democratic legitimacy and transformative potential of CAs. Narrow technical frames can exclude valid perspectives and policy options and close down debate on broader systemic and potentially more transformative issues. Conversely, such ‘system-supporting’ framings may yield more specific and applicable policy recommendations, increasing the likelihood of implementation. In this study, we present a framework and approach to analyse framings in climate assemblies. We apply this framework to examine the evidence provided to a German, a UK and a Global citizen assembly. Our analysis suggests that despite differences in scale, remit and commissioning bodies, evidence in these three assemblies had a similar range of framings. General evidence most frequently incorporated frames related to safety, governance, and fairness. Although all assemblies incorporated some degree of system-challenging frames, many of them were used little. Topic-specific evidence on energy in both the German and UK assemblies almost exclusively used energy technologies frames, potentially at the expense of critical perspectives. Interestingly, we did not observe major differences in the amount of system-challenging frames used between the assemblies commissioned by civil society actors and those commissioned by parliament; however, we observed some differences in the way some frames were used. We propose that integrating system-challenging frames with actionable steps could enhance the transformative potential of future assemblies. Our framework can be used to study how the framing of evidence influences deliberations and outcomes and to assess assemblies’ claims to provide balanced information.