While taking notable incremental steps forward, Parties to the United Nations Framework Convention on Climate Change (UNFCCC) have so far, in aggregate, been unable to scale up their ambition to mitigate climate change so as to hold a rise in global average temperature below 2° Celsius above pre-industrial levels. In this introduction to the special issue, it is posited that the UNFCCC has played and should continue to play an essential role in instigating and coordinating a global response to climate change. However, in the face of continuing difficulty in stabilizing the global climate at safe levels, it is argued here that the UNFCCC is by no means alone in addressing this challenge and that wider international cooperation is possible in a way that complements the international climate negotiations. This article shows how a variety of international institutions outside of the UNFCCC have sought – albeit with modest results to date – to address climate change, and indicates how these institutions could be enhanced to deliver greater climate change mitigation benefits. It then illustrates how these institutions may interact with the UNFCCC process, and examines the role of the UNFCCC in ensuring that the various institutions work in a complementary fashion.