The inhibition efficiency of aspirin (acetylsalicylic acid-ASA) against copper corrosion was investigated in 0.5 M HCl solution at room temperature by using electrochemical techniques. Furthermore some quantum chemical calculations were done to explain the inhibition mechanism of ASA. It was found that ASA has a promising inhibitory action against corrosion of copper in the medium investigated. The polarization curves of ASA were obtained from electrochemical measurements. According to potentiodynamic results, ASA inhibits the corrosion process of the copper cathodically and its ability as a corrosion inhibitor is enhanced as its concentration is increased. The Tafel extrapolation method was used to calculate some corrosion parameters, such as corrosion potential (E-corr), corrosion current (I-corr), cathodic Tafel slope (beta(c)) and anodic Tafel slope (beta(a)). Additionally, Langmuir adsorption isotherm was used to explain the adsorption behavior of ASA on copper surface. The adsorption equilibrium constant (K-ads) and the standard free energy of adsorption (Delta G degrees(ads)) were calculated from Langmuir adsorption isotherm. It can be concluded that the adsorption of ASA on the copper surface contains mostly physisorption but also chemisorption thereby it is so called a mixed. The quantum chemical calculations have been performed on ASA for neutral and protonated forms by using density functional theory (DFT) in gas and aqeuous phases to explain the behavior of ASA as a corrosion inhibitor. These calculated quantum chemical parameters were compared to each other and the relationship between calculated parameters and corrosion inhibition mechanism of ASA is analysed.