Abstract: The iron and steel industries generate large amounts of unavoidable CO₂ emissions as well as considerable quantities of slags. More than one-half of the emitted CO₂ is produced in blast furnaces during ironmaking, and thus it is meaningful to use blast furnace slags to capture CO₂ while addressing the byproducts and flue gas of ironmaking. Mineral carbonation of slags is a promising route to achieve carbon neutrality and effective slag utilization. To exploit slag more effectively and capture CO₂ in flue gas, an in-depth investigation into the carbonation of blast furnace slags generated with different cooling methods was conducted. The effects of the solid–liquid ratio and introduced CO₂ concentration on carbonation were determined. The CO₂ uptake capacity of air-cooled slag (0.04 g/g) was greater than that of water-quenched slag. The CO₂ uptake capacities of the two slags were comparable with those of slags in previous works, indicating the potential of the two slags for CO₂ sequestration and utilization even with low-energy input and this fact suggests that this process is feasible.