The inhibitor 2,5-dimercapto1,3,4-thiadiazole shows 94.48 percent inhibition efficiency in controlling corrosion of copper in 3.5%NaCl solution at pH 7.0. The mechanistic aspects of corrosion inhibition, based on the results obtained from the weight loss method, potentiostatic polarization study, AC-impedance study, UV-visible absorption study and surface study by FTIR, ESCA and SEM have been discussed. The inhibitor 2,5-dimercapto-1,3,4-thiadiazole appears to inhibit corrosion process through formation of protective film which was found to consist of Cu(I)-inhibitor complex, cuprous chloride, CuCl or CuCl(2)(-) complex ion or both and no oxide of copper on the surface.