The corrosion inhibition effects of benzamide (BA) and 4-aminobenzenesulfonamide (ABSA) for copper in 1.0 M hydrochloric acid (HCl) solution were investigated using potentiodynamic polarization, cyclic voltammetry (CV), and potentiostatic current-time curves. The Langmuir adsorption isotherms of the inhibitors were used to explain the adsorption behavior. In addition, surface analysis of copper was investigated using scanning electron microscopy (SEM). The results showed that the inhibition efficiency of ABSA was much better than those of BA. The theoretical study on the corrosion inhibition efficiencies for neutral and protonated forms of the BA and ABSA molecules were performed using density functional theory (DFT) and MP2 method in gas and water phases.