This study examines usage of benzotriazole (Bt) and N-mesyl benzotriazole (BtSO₂CH₃) for im- provement of corrosion resistance of low carbon steel (LCS) in 0.1 M sulfuric acid (H₂SO₄). The inhibitor effect of Bt and BtSO₂CH₃ on the corrosion behavior of LCS was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and polarization resistance techniques. Under investigated experimental conditions these compounds showed a good corrosion inhibition. The inhibition efficiency of BtSO₂CH₃ was more than that of Bt. The potentiodynamic polarization curves indicated that compounds are mixed type inhibitors. The inhibiting properties of compounds were found to depend on the concentration. The adsorption mechanism of compounds was investigated using different adsorption isotherms. The equilibrium constants and free energies of adsorption using the adsorption isotherms were calculated.