Inhibition ability of green tea extract (GTE) on the C38 steel (CS) in 1.0 M HCl was evaluated using different methods such as: weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods at various temperatures. Polarisation curves show that GTE acts essentially as mixed-type inhibitor controlling cathodic and anodic reactions with slight predominant in cathodic branches. EIS results indicate the increase of resistance transfer (Rt) while double layer capacitance (Cdl) decrease in the rise of green tea extract (GTE) concentrations. Obtained results also showed that the inhibition efficiency decreased with a rise in the temperature. Activation energy (Ea), enthalpy (ΔHa*) and entropy and (ΔSa*) of corrosion process were estimated using experimental measurements. © 2017 The Authors.