Foaming and foam stability of impure aqueous diethanolamine (DEA) solution were evaluated. The impurities used in the experiments were gas oil, normal hexane, iron oxides, and bicine. Bikerman's method was selected to study the foaming phenomenon. A predetermined quantity of impurity was added to aqueous DEA solution and pure CO2 was allowed to flow into the solution with a constant flow rate which resulted in the formation of a height of foam bubbles on the gas-liquid interface. At the equilibrium height of the foam, the foaming index of the impure solutions was calculated for different impurities and compared. The shrinking speed of the foam and the foam half-life were recorded as foam stability parameters. The presence of liquid hydrocarbons and iron oxide in DEA solution intensified solution foaming more than other impurities. To predict the parameters influencing foam stability, a mathematical model was developed.