The diversification of actors in global climate governance may entail risks, but it is also linked to enhanced democratic performance and opportunities for innovation. To what extent has this diversification fostered a parallel multiplication of perspectives in urban climate policy? To answer this question, we analyze the evolution of urban narratives based on 463 international policy documents issued between 1946 and 2020. Our analysis shows that, instead of leading to diversification, the proliferation of actors is accompanied by a growing homogenization of urban narratives. Language appears to become progressively uniform across organizations and over time, with approaches emphasizing multi-actor governance, integrated planning, and co-benefits becoming dominant. Three factors explain this homogenization. First, actors with a long history of involvement in international development exert a significant amount of influence. Second, there is a tendency toward language harmonization in international policy. Third, urban climate narratives stabilize through association with broader policy paradigms. In conclusion, the diversification of actors in international climate policy is mediated by processes of narrative alignment, which foreclose possibilities for divergent thinking.