The corrosion inhibition of mild steel in HCl by pineapple leaves extract was studied using weight loss and hydrogen evolution methods at 30-60 A degrees C. It was found that the pineapple leaves extract inhibited the acid induced corrosion of mild steel. The inhibition efficiency increases with increase in the extract concentration and with rise in temperature. Adsorption of the extract was found to obey Langmuir adsorption isotherm at all the concentrations and temperatures studied. The mechanism of chemical adsorption is proposed from the trend of inhibition efficiency with temperature. The proposed mechanism was also corroborated by kinetic and thermodynamic parameters obtained.