Pyrazinecarboxylic acid (PCA) was examined as a potential corrosion inhibitor for mild steel (MS) in 0.5 M HCl environment. The methods of electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), as well potentiodynamic (PD) polarization were utilized. Furthermore, atomic force microscopy (AFM) and quantum chemical calculations were utilized. PD polarization curves demonstrated that PCA exhibited mixed inhibitor behavior. Scanning electron microscopy (SEM) offered the creation of an adsorptive layer on the surface of MS which prevented the steel against corrosive specimens. Furthermore, density functional theory (DFT) presented good agreement with electrochemical experimental results. The adsorption equilibrium constant (k(ads)) value was calculated to be 3.704 x 10(4) M-1 which was related to a high proportion of inhibitor on the surface. In the presence of 1.0 mM PCA, inhibition efficiency was determined as 95.2% from EIS results.