In this study, the anti-corrosion capability of Houttuynia cordata leaf extract (HLE) in HCl 0.1 M on mild steel was investigated by electrochemical testing methods consisting of potentiodynamic polarization (PD), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and surface analysis including scanning electron microscope (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed an increase in corrosion resistance of steel with increasing HLE concentration and suggested that its action as a mixed-type inhibitor, resulting in excellent inhibition efficient of HLE on steel surface and lower corrosion rate. Surface analysis exhibited profoundly influential impact of HSL components for improving steel surface protection by protective film formation via adsorption process of HLE components. The steel surface protection mechanism was also provided and discussed in detail.