The corrosion inhibition of 2-mercaptobenzimidazole on A106 carbon steel and its stability in a post-combustion CO2 capture system with application of 5 M monoethanolamine aqueous solutions has been evaluated by linear polarization resistance, electrochemical impedance spectroscopy, immersion corrosion testing, scanning electron microscopy/energy dispersive spectroscopy, x-ray diffraction, and liquid chromatography-mass spectroscopy. Although no notable layer of protective corrosion product was found on the A106 surface at 80°C and atmospheric pressure for >180 h, corrosion was inhibited, and its polarization resistance increased nearly an order of magnitude when 2-mercaptobenzimidazole was added. However, degradation of 2-mercaptobenzimidazole, associated with the formation of an FeS layer with cracks, occurred at 108°C and 4.13×105 Pa.