Science has played a key role in the development of climate change policy. Although action has been slow to materialize, climate change is firmly on the policy agenda internationally and domestically in many countries across the world. Climate scientists have helped put the issue into policy agendas, and climate change science is expected to provide the basis for policy action on mitigation and adaptation. However, science and policy sometimes have an uneasy relationship, as highlighted by fraught political debates over climate change. Issues of uncertainty, complexity and politics all influence the interactions and result in a range of different roles for scientists. At the same time, it is not simply policy-makers wanting and using science: campaigners, industry, communities and a range of other stakeholders all want to use science to influence policy. The interactions are not one-way, but multifaceted, and the line between science, policy and politics can be increasingly blurred. As a result, collaborative, co-learning approaches are needed to improve the use of science in policy. Drawing on the authors’ research, this chapter will discuss the challenges faced at the boundaries between science and policy and highlight how collaboration and collective action might be deployed to manage the interface. This can both help researchers better design their research to support decision-making and help decision-makers and other stakeholders improve their use of science for evidence-based policy-making.