This paper presents novel empirical evidence on the internationalization of green R&D by multinational firms (MNCs), as measured by patents data. Using data on inventors’ addresses for the set of 1,200 MNCs firms patenting in green technologies over the 2004-2009 period, we find that about 17% of green patents result from MNCs R&D investments conducted outside their home countries. MNCs tend to locate their foreign green R&D activities in other OECD markets and in China, in particular in lightings and solar technologies. The empirical analysis reveals that the probability of conducting green R&D abroad increases with the host country’s stringency of environmental regulation, market size and (green) R&D intensity. Also, relatively lower wages for scientists and engineers, and stronger protection for intellectual property rights in the host country increase the likelihood for MNCs to offshore green R&D. The paper concludes by discussing the policy implications of this changing global innovation landscape.