The aim of this work was to investigate the inhibition effect of acid garlic essential oil (GO oil) as an inhibitor on the corrosion of carbon steel in a 1M HCl solution at different temperatures by weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The GO oil acts as an effective corrosion inhibitor for carbon steel in a hydrochloric acid medium. The inhibition process is attributed to the formation of an adsorbed film of inhibitor on the metal surface which protects the metal against corrosion. The result indicates that the inhibition efficiency) increases as with the concentration of the inhibitor. The (%IE of GO oil depends on its concentration, and attains approximately 95.8% for 2.5 g/L at 298K. The effect of temperature on the corrosion behavior of carbon steel in 1 M HCl, with the addition of essential oil was also studied. The adsorption of the essential oil on the carbon steel surface obeyed the Langmuir adsorption isotherm. Values of inhibition efficiency calculated from weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy are in good agreement. Polarization curves showed that GO oil behaves as a mixed-type inhibitor. The activation energy as well as other thermodynamic parameters for the inhibition process was calculated and discussed. The results obtained showed that the acid garlic essential oil could serve as an effective inhibitor of the corrosion of carbon steel in hydrochloric acid solutions. © 2014 The Authors.