This article hypothesizes that the material incentives associated with the clean development mechanism (CDM) have contributed to the internalization of climate protection norms in China. In current academic research, the CDM has both been extolled as a cost-effective and vilified as an environmentally and ethically inadequate climate mitigation instrument. Few studies so far, however, have looked into the CDM’s potential contribution to socialization-related phenomena such as raising climate change awareness in emerging economies. The relationship with the EU is highly relevant in this context, as the emission reduction credits (CERs) resulting from CDM projects would not have had any meaningful prices without the European Union’s Emissions Trading System (EU ETS). This article aims to fill the current research gap by studying the socialization potential of the CDM in EU–China climate relations in four periods, namely initiation (2001–2005), improvement (2005–2007), consolidation (2008–2010) and habit formation (2010–2014). We argue that there is at least a discernible effect and that the underlying causal mechanism involves the emergence and activities of norm entrepreneurs and habit formation through a process of legal institutionalization.