This chapter explores the evolution and the implications of the debate about climate change at the UN Security Council, from the first open meeting in April 2007 to the one in December 2021, which saw the rejection of a draft resolution aimed at consolidating the role of the Council in dealing with climate change. Despite the contested debate, climate change has been incorporated in several aspects of the Council’s work. The chapter analyses these developments through the lenses of securitization and climatization. While failing to mobilize exceptional measures, as securitization would suggest, the climate security discourse has been framed according to the specific competencies of the Council. Hence conflicts (seen as those mainly located in the Global South) and peacekeeping play a dominant role in the discussion. States remain central, even if framings in terms of human security and threats to humanity are also often used. At the same time, the debate has contributed to a transformation of the understanding of security and of the role of the Council through a process that scholars have defined as a climatization of the security field and is contributing to establishing a specific climate security field.