This study aims to assess the governance capacity of Transnational Municipal Networks (TMNs) active in climate policy. For this purpose, I perform an Event History Analysis (EHA) and two case studies, testing the impact of network membership on the likelihood of a city adopting a local climate strategy. In a fist step, I develop the argument that TMNs influence their constituent’s decision-making through governance by diffusion, meaning that they devise strategies to accelerate policy spread among their members in general, and the spread of local climate strategies in particular. In a second step, I derive a range of alternative explanatory factors from theory, including policy diffusion along regional clusters, the coordinative impact of decisions on superordinate political levels, and local factors like a municipality’s financial resources, potential cost savings, and perceived local vulnerability to the repercussions of climate change. I then test these factors against each other. First by performing an EHA on a unique data set containing information on 274 European cities for the time period between 1992 and 2009, and secondly by examining the cases of Hanover and Offenbach, a pioneer and a latecomer in the adoption of a local climate strategy. The results of EHA show that TMN membership is indeed the prime motivator for a city’s adoption of a local climate strategy, mainly because networks succeed in facilitating learning processes among their members. Climate policy programs on superordinate political levels are equally important, especially for latecomers. The case studies confirm that TMNs are a key resource of knowledge and expertise for both pioneers and latecomers. Support from the national government did not play a role in Hanover’s decision to introduce a local climate strategy, however, it allowed Offenbach to make a qualitative leap in the elaboration of its action plan. Cost savings did not motivate the decision to act on climate change. Rather, it served city administrations as an argument to persuade local citizens and businesses to become active on their part.