Carbon dioxide was absorbed into aqueous polyethylene oxide (PEO) solution containing diethanolamine (DEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PEO on the chemical absorption rate of CO2, where the reaction between CO2 and DEA was assumed to be a first-order reaction with respect to the concentration of CO2 and DEA, respectively. A unified correlation equation containing Deborah number, which reflects the viscoelastic properties of the non-Newtonian liquid, was used to obtain the volumetric liquid-side mass transfer coefficient of carbon dioxide in aqueous PEO solution. The elastic properties of PEO accelerated the absorption rate of CO2 compared with that of a Newtonian liquid based on the same values of viscosity.