This study investigates the reactivity of municipal solid waste incineration residues (MSWIr) to aqueous carbonation, focusing on CO2 absorption rates, uptakes, and heavy metal (HM) leachability. Various combinations of boiler, electrofilter, and bag filter residues were assessed under typical incineration conditions. Bagh filter residues from lime-sorbent plants exhibited the highest CO2 uptake (244.5 gCO2/kg), while bottom ashes (BA) fine fraction, boiler/electrofilter fly ashes (FA), and other mixed air pollution control residues (APCr) demonstrated uptakes of 101, 0, 93, and 167 gCO2/kg, respectively. Carbonation kinetics revealed that high calcium content FA and APCr, followed similar CO2 absorption trends. Notably, BA carbonation was predominantly driven by Ca-aluminates rather than lime. Carbonation reduces leaching of Al, As, Cd, Co, Cu, Ni, Pb and Zn compared to water washing, though significant concerns arise with anions such as Sb and Cr. In BA, critical behaviours of Cr, Mn, and Fe were observed, with Cr leaching likely controlled by Fe-Mn-Cr oxide particle dissolution. These findings highlight the potential of integrating EMR through density or magnetic separation in BA prior to carbonation to reduce HM leaching and recycle critical metals (Ag, Cu, Cr, Ni, Mn, etc).