Inhibition of corrosion processes of copper in aerated 3.5% NaCl solutions by 5-(3-aminophenyl)-tetrazole (APT) has been investigated using open-circuit potential, potentiodynamic polarization, potentiostatic current–time, electrochemical impedance spectroscopy, and weight loss measurements together with pH and Raman spectroscopy. Increasing concentrations of APT greatly decreased the corrosion rate and increased the surface and polarization resistance. It was concluded that the adsorption of APT blocks the active sites on the copper surface leading to the formation of cuprous chloride and oxychloride complexes. This was supported by the Raman spectrum obtained from the copper surface after 24 days of immersion in a 3.5% NaCl solution containing 5.0 mM APT. The results collectively are in good agreement and show clearly that APT is a good corrosion inhibitor for copper under the conditions studied.