Abstract Wet mechanochemical processing of olivine under a CO2 atmosphere promotes the CO2 sequestration in the form of MgCO3 and the CO2 reduction to CH4 at room temperature. The effects of milling time and CO2 pressure on the CO2 storage and CO2 reduction were evaluated at lab-scale. Wet mechanochemical introduces progressively significant morphological, structural, microstructural, and textural changes in olivine for prolonged milling times, inducing fast carbonation reaction after 15 min of ball milling. Long milling times stimulate the CO2 conversion to CH4 and decrease the carbonation reaction rate, because both reactions occurred simultaneously. The CO2 sequestrated as MgCO3 is about 4.83 wt% and 6.81 wt% for 1.0 atm of CO2 after 120 min and 180 min of milling using different CO2 charge strategy. The amount of CO2 reduced to CH4 was 24 and 33 mmoles/kg of olivine after 120 min with 1.0 and 1.5 atm of CO2, respectively. Wet milling of olivine in CO2 atmosphere is a technique with potential for large-scale carbon mineralization.