A significant number of countries classified as “developing” during the negotiation of the UNFCCC in the early 1990s have experienced rapid economic growth and increase of greenhouse gas emissions since then. We assess whether governments of such countries are considering taking up responsibility for emissions mitigation in the context of the UNFCCC’s principle of common but differentiated responsibility (CBDR). While an expansion of mitigation responsibility to Non-Annex I countries has been strongly opposed by overarching groups such as the G 77, we find countries such as South Africa and Indonesia that have clearly supported binding commitments. Other countries like China and Singapore oppose binding commitments but increasingly engage in domestic mitigation action. Moreover, China has pledged a significant amount of climate finance. Even in the countries of the Gulf Cooperation Council, which adamantly refuse mitigation commitments, some mitigation action seems to emerge. We thus foresee that countries will increasingly adopt differentiated positions regarding their responsibility for mitigation. This could provide new dynamics in international climate negotiations.