Climate policy is a new area of European integration, although there were no exact references to the issue of climate change in the Maastricht Treaty. However, this article draws attention to the interesting coincidence of the creation of the European Union (EU) in the 1990s and the consequences of the Earth Summit in Rio de Janeiro which started the process of greening the EU Member States’ foreign policies and enhanced the importance of environmental and climate protection issues on the international agenda. The Member States and EU institutions, acting within the institutional framework defined by the Maastricht Treaty, in the face of the limitations resulting from unanimous voting in taxation policy, started to develop climate policy (in particular, the EU Emissions Trading System), mainly based on environmental law, enabling decisions to be taken by a qualified majority. The growing importance of climate policy in the EU was influenced by many factors and the different motivations of individual Member States and other European policy actors. After depicting the main causes and effects of the growing importance of EU climate policy, the article discusses the most important challenges facing the EU with regard to the implementation of an ambitious climate policy. In recent years, one of the main reasons for this increase is the fact that each of the successive overlapping crises (concerning migration, pandemic, Russia–Ukraine war or spiking energy prices) is a suitable opportunity to strengthen EU climate policy.