This work focuses on the development of a new solvent for CO2 capture. This new solvent is an aqueous solution with a blend of N-methyldiethanolamine (MDEA) and triethylene tetramine (TETA), an amine with four amino groups. CO2 absorption was investigated between 298 and 333 K using a Lewis cell with a constant interfacial area. Several concentrations of MDEA (17.5 and 40 wt %) and TETA (3 and 6 wt %) were assessed. The influence of the CO2 partial pressure on the absorption rate was pointed out. The addition of small amount of TETA leads to a high increase in the CO2 absorption rates. A numerical model based on the film theory was used to determine the rate coefficients between CO2 and TETA for the different solvents. The physicochemical parameters have a huge influence on the determination of the rate coefficients.