There are debates on whether the implementation of the Belt and Road (BR) initiative could significantly increase CO₂ emissions in participating countries. Nevertheless, the policy effect of the BR initiative on both consumption- and production-based CO₂ emissions has not been fully explored. In this study, we quantified the consumption- and production-based CO₂ emissions in BR countries with a multiregional input–output model. Then, a difference-in-differences (DID) model was used to identify the CO₂ emissions caused by the BR initiative. Results showed that the production-based CO₂ emissions (20.77 Gt) were 11 percent higher than the consumption-based CO₂ emissions (18.71 Gt) in BR countries. The BR initiative had a significant, positive effect on per-capita consumption-based CO₂ emissions (p value < 0.1), with an average increase of 0.51 t/cap/year, but had no significant effect on per-capita production-based CO₂ emissions (p value > 0.1). These results imply that the BR initiative promoted regional consumption to achieve common prosperity and boosted green transformation of regional economy. Moreover, non-BR countries that have consumed CO₂-embedded products should take responsibility for the CO₂ emitted in BR countries. Participants should give priority to strengthening the cooperation based on their country’s infrastructure conditions rather than the proximity to China. These findings clarify the policy effect of the BR initiative and distinguish the CO₂ emission responsibility from both consumption- and production-based perspectives.