Substantial and increasing amounts of funding are available for countries to undertake climate change interventions. This article argues that to ensure effective allocation of these resources, the selection and design of climate change mitigation and adaptation interventions should be based on evidence of what works, what doesn't work, under what circumstances and at what cost. Currently the evidence base on the impact of climate change interventions is minimal and there is a need for wider application of rigorous impact evaluation (IE) in the field. Climate change interventions have much to learn from experiences in related fields, notably international development and conservation. The paper highlights some of the challenges faced when conducting IEs of climate change interventions and discusses how these can be tackled. Moreover, it discusses some of the key areas of mitigation and adaptation interventions and suggests how IEs could be implemented, using IEs from other policy fields as examples. It arg...