The precautionary principle is one of the central principles of environmental law. Its relevance, however, extends far beyond environmental protection and shapes many areas of risk regulation. Yet its meaning for climate law has received only limited attention. Climate change presents a distinctive case of precaution. It requires action under conditions of uncertainty to prevent serious and irreversible harm. Unlike classical fields of precaution, which deal with specific and contained risks, climate change affects all sectors and spans generations. This paper outlines the legal basis and dimensions of the precautionary principle and develops key elements for a precautionary approach to climate law.