Carbonation profiling of cementitious materials is traditionally based on the phenolphthalein test, which often underestimates actual carbonation depth and provides limited insight into moisture redistribution and pore structure evolution. In this study, proton nuclear magnetic resonance relaxometry (1H-NMR) was employed as the principal tool to establish a comprehensive carbonation profile of white Portland cement (WPC) and metakaolin-blended cement with a water-to-binder ratio of 0.5 and exposed to accelerated conditions with a CO2 concentration of 3%. Using hydrogen nuclei in water as probes, 1H-NMR enabled direct quantification of water content and allowed quantitative characterisation of pore structure evolution. Combined with thermogravimetric analysis (TGA), a more precise determination of the carbonation progress can be made. Results show that carbonation induces depletion of mobile water and a reduction in total pore volume. These findings demonstrate that 1H-NMR is a powerful tool for studying the water redistribution and microstructural evolution during carbonation.