Co-benefits rarely enter quantitative decision-support frameworks, often because the methodologies for their integration are lacking or not known. This review fills in this gap by providing comprehensive methodological guidance on the quantification of co-impacts and their integration into climate-related decision making based on the literature. The article first clarifies the confusion in the literature about related terms and makes a proposal for a more consistent terminological framework, then emphasizes the importance of working in a multiple-objective–multiple-impact framework. It creates a taxonomy of co-impacts and uses this to propose a methodological framework for the identification of the key co-impacts to be assessed for a given climate policy and to avoid double counting. It reviews the different methods available to quantify and monetize different co-impacts and introduces three methodological frameworks that can be used to integrate these results into decision making. On the basis of an initial assessment of selected studies, it also demonstrates that the incorporation of co-impacts can significantly change the outcome of economic assessments. Finally, the review calls for major new research and innovation toward simplified evaluation methods and streamlined tools for more widely applicable appraisals of co-impacts for decision making.