This article explores the prospects for joint leadership by the United States (US) and the European Union (EU) in an evolving multipolar world. Arguing that multipolarity leads to a highly differentiated global system, it conceptualizes global order as negotiated order revolving around issue-specific global governance arrangements subject to constant negotiation processes. In this context, transatlantic leadership depends not only on a US and EU willingness to lead individually and collectively, but especially on their capacity to define joint purposes and mobilize followers in issue areas relevant to global order. To test whether the two parties fulfil these conditions, the article first engages in a discourse analysis comparing US and EU leadership ambitions and visions of world order as expressed in their global strategies. US and EU rhetoric is subsequently compared to their (inter)action in the major global policy domain of climate change, focusing on the negotiations of the 2015 Paris Agreement. The article finds that opportunities for US-EU leadership generally exist, but that sustained future leadership will depend on renewed commitments and tend to be, rather than cross-cutting and relatively stable as during the Cold War, issue-specific and contingent, necessitating regular negotiation with other major global forces.