The need for a clear research and policy agenda to assist early stage Cleantech financing has never been greater. These businesses may hold important keys to unlocking vital globally game changing technologies to tackle climate change. The paper provides an overview of recent academic literature and proposes a research agenda for early stage Cleantech SME finance. With growing interest in how to support innovations that tackle the climate emergency, there is a need for evidence that can assist the private sector, civil society organizations and policymakers in finding more effective ways to encourage impact investing and other finance for early stage Cleantech SMEs. This research agenda will therefore contribute to sustainability transitions in key sectors and the development of a sustainable low carbon economy.