The methanolic extract of Peumus boldus (P. boldus) has been studied as a potential green corrosion inhibitor for carbon steel in 0.5 M H 2 SO 4 using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy tests at 25, 40 and 60°C, and concentrations of 0, 0.1, 0.3, 0.5, 0.7 and 1.0 g/L. Results indicate that P. boldus is physically adsorbed onto the steel surface and acts as a mixed corrosion inhibitor of carbon steel corrosion. The data fitted best to the Temkin adsorption isotherm. The inhibition efficiency of P. boldus extracts was observed to increase with increasing its concentration but decreases on increasing the test temperature. The inhibitive effect is attributed to the presence of vitamin E, Limonene and eucalyptol in the extract.