Climate negotiators in Cancún reached agreement that long-term climate finance will include a commitment by developed countries to mobilize US$ 100 billion per year to help developing countries combat climate change. However, that level of investment will require substantial capital from private investors, particularly for innovation and commercialization. We propose a public-private green venture fund (GVF) to promote development and deployment of low-carbon technologies for developing countries. The GVF will use a fund of funds model backed by public “cornerstone” equity. In this paper, we propose a structure for the GVF and explain the design rationale, operating principles and key parameters for two funds of funds for technology innovation and deployment. We also highlight some key issues to be considered, including differential treatment of public and private investors and possible approaches to setting technology priorities.