Abstract Synergies and trade-offs exist between climate mitigation actions and target indicators of the Sustainable Development Goals (SDGs). Some studies have assessed such relationships, but the degree of such interaction remains poorly understood. Here, we show the SDG implications associated with CO₂ emissions reductions. We developed ‘marginal SDG-emissions-reduction values (MSVs)’, which represent the marginal impacts on SDG indicators caused by a unit CO₂ emissions reduction. This metric is applicable to national assessments and was applied to Asia. We found clear relationships between CO₂ emissions reduction rates and many SDG targets. For instance, 1% reduction of CO₂ can avoid 0.57% of air pollution-related premature deaths (SDG3), whereas the mean species richness (SDG15) is decreased by 0.026% with the same reduction (not including climate change impacts). Our findings are useful for assessing the SDG implications associated with CO₂ emissions reduction targets, which will help inform national climate policies.