The aim of this chapter is to explore when and how climate change became an issue of social justice in international climate negotiations. We argue that around the turn of the millennium, climate change went from primarily being framed as natural science and a technical issue that suggested market-based approaches as remedy for the crisis, to being framed as an issue where climate justice took centre stage. This shift consisted of new ways of talking and thinking about climate change, a discursive shift that placed emphasis on global justice and anti-capitalist criticism. The chapter mainly analyses the period from the implementation of the United Nations climate agreement (UNFCC) in 1992, to the climate negotiations in Copenhagen in 2009, where the struggle for climate justice was popularised on the international political scene. Empirically, our primary focus is on the UN’s climate negotiations and what we, consistent with the research literature, refer to as the international climate justice movement.