The corrosion of inhibition of mild steel has been monitored by Ethane-2-thioamido-4-amino-N-(5-methylisoxazol-3-yl)-benzene sulfonamide (ETAMBS) as an inhibitor in 1NHCl medium. The potentiodynamic polarization studies demonstrated the mixed mode of inhibitive action of the compound. The parameters like charge transfer resistance, double layer capacitance, surface uniformity and relaxation time derived from impedance analysis confirmed the effective performance of the inhibitor. The mode of adsorption of ETAMBS on mild steel surface was well demonstrated from quantum mechanical functions such as HOMO, LUMO, Hardness, softness, energy gap and dipole moment. The formation of protective film of the compound was proved by SEM images. © 2013 University of Manchester and the authors.