In the present work, 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT) was synthesized and characterized using FTIR and ¹H NMR. The triazole was for the first time investigated as a novel corrosion inhibitor for copper in 3.5% NaCl solution employing the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The AMTT showed a corrosion inhibition efficiency of >94% at a concentration of 0.5 mmol L⁻¹ and behaved as a mixed type inhibitor with cathodic predominance. The influence of AMTT on the kinetics of the oxidation-reduction behaviour of copper in 3.5% NaCl was studied using cyclic voltammetry. The protective film of AMTT on the copper surface was studied in detail using time of flight-secondary ion mass spectrometry (ToF-SIMS), AFM and FTIR-ATR. The results of surface analysis suggested chemical adsorption of AMTT over copper surface. The inhibitor AMTT is found to interact with the copper surface via the sulphur atom of the thiol group and the nitrogen atoms of the amino group and the triazole ring. ToF-SIMS data also suggest that the inhibitor may bind to two copper surface atoms. The results of theoretical studies via pKa analysis and the quantum chemical calculations support the experimental observations.