Amine-functionalized materials have been widely investigated as promising candidates for CO2 capture. However, they are prone to degradation in the presence of O-2, resulting in loss in the CO2 capture ability as well as a decrease in the sorbent lifetime. In this study, we evaluated the effect of different oxidation inhibitors on degradation of polyamines, including tetraethylenepentamine- and polyethylenimine-impregnated mesoporous silica. Sulfur-containing compounds and traditional antioxidants were selected as additives. Oxidative degradation tests of the amine solid sorbents were performed in a packed-bed reactor equipped with a temperature controller. The results showed that traditional antioxidants, such as butylated hydroxytoluene, N,N'-diphenyl-1,4-phenylenediamine, N,N'-di-2-butyl-1,4-phenylenediamine, 2,2'-thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], catalyzed oxidative degradation. In contrast, sulfur-containing additives, which owe their effectiveness to free-radical scavenging and peroxide decomposition actions, decreased the oxidation rate. Amine solid sorbents containing such additives had 1.5-2 times higher CO2 adsorption capacity retention values than the nonadditive sorbents under accelerated oxidation conditions. Furthermore, the long-term stability of the amine solid sorbents over 15 months storage was demonstrated. These sulfur-containing additives also delayed sorbent degradation.