This guidebook provides practical and operational guidance on how to assess and overcome barriers facing the transfer and diffusion of technologies for climate change mitigation and adaptation. The guidebook is designed to support the analysis of specific technologies, instead of pursuing a sectoral (e.g. transport) or technology group (e.g. renewable energy) approach. Given that there is no single solution to enhancing technology transfer and diffusion, policies need be tailored to country-specific context and interests. Therefore, the guidebook presents a flexible approach, identifying various assessment options and tools for analysts and decision-makers.