Climate alliances like the Climate Council Jönköping have a big impact on combating environmental issues on a local level. Research shows that communication plays a crucial role in such cross-sector partnerships to enhance the collaboration between its members. This thesis wants to explore the impact of climate alliances on their members’ sustainable communication and CSR initiatives, using the example of the Climate Council Jönköping. Based on different theories, namely Communication Constitutes Organization Theorizing, the Model of CSR Implementation, and the Value Belief Norm Theory of Environmentalism, the aim was to contribute knowledge to the research fields of sustainable communication, CSR, and collaboration. To explore the existing research gap, twelve semi-structured interviews with experts from different member organizations of the Climate Council were conducted. By applying qualitative content analysis, it became visible that the Climate Council’s impact on communication and CSR efforts differs among the members. On the one hand, it can be difficult to include the campaigns of the council into one’s own communication. On the other hand, the membership raises awareness about sustainability and environmental topics and enables collaboration and knowledge exchange through cross-sector partnerships. Based on the findings, it can be recommended to the Climate Council to provide more communication material for the members for easy integration. Additionally, more events can increase the visibility of the council and raise awareness for local cross-sector collaborations to tackle environmental problems, enable new networking options, and establish innovative partnerships.