In this study, the adsorption and corrosion inhibitive properties of ethanol extract of Dialium guineense leaves for mild steel in 0.5M HCl was studied using gravimetric method. The results obtained showed that the ethanol extract of Dialium guineense leave is a good adsorption inhibitor of Mild Steel in 0.5M HCl. The inhibition efficiency was found to increase with increase in the concentration of ethanol extract of Dialium guineense leave but decreased as the temperature increases. The inhibition efficiency increases up to a maximum of 92%. The kinetic study was found to follow pseudo first order reaction with high correlation. Thermodynamic consideration reveals that adsorption of ethanol extract of Dialium guineense leaves on mild steel surface is exothermic, spontaneous and fitted the Langmuir adsorption isotherm. The value of activation energy and Gibb’s free energy obtained were within the range of limits expected for the mechanism of physical adsorption.