2-mercaptobenzothiazole (MBT) is known as an efficient corrosion inhibitor for copper. In the present work, we performed quantum chemical DFT calculations of the interaction of MBT on Cu(111) surfaces covered by an ultrathin Cu2O(111) film, in order to bring atomic scale insight on the corrosion inhibition properties of MBT on oxidized copper surfaces. Thione and thiolate forms of MBT are found to interact strongly with the oxidized surfaces. The formation of a monolayer at full coverage is favored over single molecular adsorption at low coverage with the molecules adopting a perpendicular orientation. Thione binds strongly via covalent bonding between the exocyclic sulfur atom and the under coordinated Cu site, and additional H-bonding between the NH group and surface oxygen atoms (NH...O H-bond). Thi-olate binds more strongly via a second covalent bond between the N atom and saturated Cu site. Bonding interaction is confirmed by the electronic structure analysis and charge transfer. The adsorption process leads to the reconstruction of the topmost oxide surface. The calculations suggest that both forms of MBT may substitute H2O and OH at the Cu2O film surface, and thus may form a protective layer on oxidized copper surfaces in aqueous environment.