Effects of 3-amino-1,2,4-triazole (ATA) on the inhibition of copper corrosion in 0.5 M HCl solutions have been studied using gravimetric, electrochemical, and Raman spectroscopy investigations. Weight-loss measurements after varied immersion periods revealed that the dissolution rate of copper decreased to a minimum, while the inhibition efficiency ( ζ % ) and consequently the degree of surface coverage ( θ ) increased with the presence of ATA and the increase of its concentration. Potentiodynamic polarization, chronoamperometric, and electrochemical impedance spectroscopy (EIS) measurements after 0, 24, and 48 h immersion of the copper electrode in the test solutions showed that the presence of ATA molecules significantly decreased cathodic, anodic, and corrosion ( j corr ) currents and corrosion rates ( R corr ) and greatly increased polarization resistance ( R p ) , ζ%, and θ; this effect was increased on increasing the ATA content in the solution. Raman spectroscopy confirmed that ATA molecules strongly adsorbed onto the copper surface, blocking its active sites and preventing it from being corroded easily.