As a kind of environmentally friendly corrosion inhibitor, the extract from pomelo peel was evaluated for C38 carbon steel in 1 M HCl solution. The corrosion inhibiting performances of the extract from pomelo peel was confirmed using electrochemical method, weight loss measurement and scanning electron microscope (SEM) observation in the temperature range between 298 and 328 K. The inhibition efficiency was found to increase with the concentration of the extract from pomelo peel. Electrochemical impedance spectroscopy (EIS) measurement indicated that the corrosion process of the steel was inhibited by the adsorption of the extract from pomelo peel, following a Langmuir-type isotherm.