This work evaluated the dynamical mechanical properties of Portland cement paste modified with cellulose microcrystalline (MCC) before and after exposition to CO2 saturated environment during 4 h. All the cement paste samples were subjected to thermogravimetrical analysis (TGA) before and after carbonation process. Changes in morphology of the samples were studied in a field emission electron microscope (FE-SEM); additionally changes generated in hydration kinetic by the addition of MCC to cement paste, were followed by measuring the adiabatic temperature during the first 24 h of reaction. The addition of MCC delayed the hydration reaction. TGA results shown that cement past with MCC was carbonated. The carbonation process in TGA was evaluated by the increase in the size of the peak around 680 °C related with calcium carbonate thermal degradation. The dynamical mechanical analysis shown that, cement paste with MCC increased significantly its storage modulus after CO2 exposition.