The inhibition of corrosion of mild steel in hydrochloric acid in the presence of Gnetum gnemon L. peel extract (GGPE) has been studied using the weight loss, potentiodynamic polarization, FTIR and scanning electron microscopy (SEM) analysis. It was found that the inhibition efficiency increased with increasing concentration of GGPE and temperature. The inhibition was assumed to occur via adsorption of inhibitor molecules on the metal surface. The adsorption of the extract on the mild steel is found to obey Langmuir adsorption isotherm and acts as a mixed-type inhibitor. Thermodynamic and kinetic parameter data for the adsorption process were calculated and discussed.