Metal corrosion is a destructive process for many industrial operations, including oil well acidizing and acid pickling. Therefore, numerous efforts made by many researchers to control the steel corrosion. In the present work, A (E)-4-(((4-(5-mercapto-1,3,4-oxadiazol-2-yl) phenyl) amino) methyl)-2-methoxyphenol (MOPM) has been synthesized and characterized as a new corrosion inhibitor for mild steel in 0.1 M hydrochloric acid. FTIR and 1 HNMR were used in the diagnosis of MOPM, while electrochemical polarization technique was employed to test the performance of inhibitor at various temperatures and inhibitor concentrations. Electrochemical studies showed that MOPM acts as a mixed-type inhibitor with a maximum inhibition efficiency of 93.2% at 30 ◦C and 0.5 M MOPM. Furthermore, the presence of MOPM increased the polarization resistance and depressed the corrosive action. The inhibitory action of MOPM over mild-steel surface was according to Langmuir adsorption isotherm. The calculated free energy of adsorption was − 20.663 kJ.mol− 1 that suggested the spontaneous physical adsorption mode. Value of activation energy was higher in the presence of MOPM, which indicated the formation of protective layer on the metal surface. Quantum chemical calculations that carried out to the chemical structure of MOPM provides a reasonable support to the experimental results