This thesis identified dominant discourses in climate change mitigation policy in three Swedish municipalities using argumentative discourse analysis. It was explored how these discourses influence the potential for success in mitigating climate change. Other studies have identified several factors that are important when working with climate change mitigation in municipalities, for example, political leadership and organizational structure. However, studies have shown that discourse is also an influential factor since it sets the frame for what can be thought of, consequently influencing policies and actions, but this has not been studied as much at the municipal level in Sweden. Previous studies of environmental policy have shown the dominance of an ecological modernization discourse, where economic growth and environmental issues are combined to create a win-win. The results in this thesis show the dominance of a strong ecological modernization where the decoupling between economic growth and environmental problems, renewable energy and technology, a global justice perspective, and a focus on collaboration between stakeholders is central. A main conclusion is that the ecological modernization discourse risks obscuring potential solutions that are not related to the market or technological innovation. However, the inclusion of a diversity of actors and a focus on justice could potentially minimize this risk. Finally, emerging discourses around transformation and circular economy could be ways to problematize the taken-for-granted ecological modernization discourse. However, their potential depends on how these concepts are framed and what is included in them.