Abstract: Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO₂-mineralized cementitious materials. In this work, copper-nickel slag-based cementitious material (CNCM) was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO₂ mineralization capacity. Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development. Meanwhile, thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO₂ adsorption amount and carbonation products of CNCM. Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging (BSE) with energy-dispersive X-ray spectrometry. Results showed that among the studied samples, the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO₂ sequestration amount of 8.51wt% at 80°C and 72 h while presenting the compressive strength of 39.07 MPa. This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO₂ and exhibit high compressive strength. Although the addition of citric acid did not improve strength development, it was beneficial to increase the CO₂ diffusion and adsorption amount under the same carbonation conditions from BSE results. This work provides guidance for synthesizing CO₂-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.