<p>CO₂-cured fly ash (FA) cementitious materials can significantly reduce carbon footprints through raw material substitution and CO₂ sequestration. Given the critical influence of pore structure on material properties, this study focuses on the effect of CO₂ curing with sufficient carbonation on the pore structure by employing mercury intrusion porosimetry (MIP), low-field nuclear magnetic resonance (LF-NMR), electrochemical impedance spectroscopy (EIS) and gravimetry method. The evolutions in the compressive strength and phase compositions are also examined. The results indicate that the pozzolanic reactions may be suppressed in CO₂-cured FA cementitious materials. The porosity in CO₂-cured FA cementitious materials has a decrease, but the coarsening phenomenon of pore structure becomes more remarkable with increasing FA content. Some connected pores may convert to disconnected large pores, while others may undergo coarsening into larger diameters. The decrease in the compressive strength of CO₂-cured FA cementitious materials is mainly attributed to substantial increases in large pore volume (&gt; 200 nm). Therefore, it needs to establish an optimization framework for CO₂ curing based on whole lifecycle assessment in further study, which should consider resulting variations in strength and durability, carbon emissions from curing equipment, environmental benefits of FA utilization, and CO₂ sequestration.</p>