The cost of carbon dioxide (CO2) sequestration by an aqueous mineral carbonation process using waste concrete was estimated. We considered scenarios where the amount of waste concrete used and the conversion ratio of calcium to calcium carbonate (CaCO3) varied in the range of 30-300 kt/y/plant and 50-80wt%, respectively. Installation of CaCO3 recrystallization equipment, which produces greater revenue, was also examined. The costs of CO2 sequestration and waste concrete treatment decreased with increasing waste concrete throughput and the conversion ratio of calcium to CaCO3. The lowest estimated cost of CO2 sequestration by the described process was -232 USD/t-CO2, and the process could sequester approximately 1.4 million t of CO2 annually, in Japan. The process can also be applied to recycling waste concrete; recycling becomes economically feasible when more than 90,000 t of waste concrete is treated by the plant annually. The proposed aqueous mineral carbonation process is highly competitive with other sequestration methods, but optimum efficiencies of scale are limited by the availability of waste concrete.