This article assesses the evolving ‘stringency’ of multilateral climate mitigation governance towards the 2015 Paris Agreement. To do so, we systematically distinguish four key dimensions of hard/soft governance: (1) formal legal status; (2) the nature of the obligations (procedural-substantive); (3) prescriptiveness and precision; and (4) implementation review and response. We find that the governance approach of the Paris Agreement is significantly softer than the 1997 Kyoto Protocol, but harder than the 2010 Cancun Agreements under the UN Framework Convention on Climate Change. As a result, the Paris Agreement has had a differentiated effect on the stringency of governance. On the one side, it has softened climate governance for countries that are parties to the Kyoto Protocol, most notably the European Union. On the other side, it has hardened the international governance framework for developing countries and industrialised countries that are not subject to the Kyoto Protocol, including the US, Japan, Canada, and Russia. The shifting climate geopolitics of the twenty-first century helps us understand this development.