Small states, led by the Republic of the Marshall Islands, spearheaded recent greenhouse gas emissions reductions at the International Maritime Organisation. This chapter documents and explains their success. We argue that it can be explained by three factors: 1) the vision of the entrepreneur; 2) development of capacity within the Republic of the Marshall Islands and the region; and 3) the commitment of key actors to create and seize opportunities in available forums, realise that vision and translate it into international support. In doing so, these small states have exploited existing norms, including the sovereign equality of states and institutional rules of international organisations, to their advantage. This case study therefore adds to the growing body of evidence that small states can influence multilateral diplomacy on certain issues and in certain international organisations despite opposition from large states and powerful vested interests.