This paper examines the effect of multilateral energy technology initiatives, so called "Implementing Agreements", on international research collaboration in seven important climate change mitigation technologies. The analysis is conducted using patent data on 33 OECD countries during the period 1970- 2009. We find that co-invention is significantly affected by the membership in the Implementing Agreement. Extending adherence to other countries would increase co-invention by about 90% in the case of wind and fuel cells, and even more in the case of biofuels, solar PV and CCS. Given the urgency to develop effective international mechanisms to mitigate climate change, these results are encouraging and the topic is an important area for further policy research.