The corrosion inhibitory potentials of Bamboosa vulgaris leaves extract in 1M HCl solution was studied using gravimetric and gasometric techniques. The results obtained from both gasometrical and gravimetric analysis showed decrease in corrosion rate of mild steel immersed in the 1M HCl solution containing Bamboosa vulgaris leaves extract from the corrosion of the mild steel immersed in the blank uninhibited 1M HCl solution. There was a more pronounced decrease in corrosion rate as the concentration of the plant extract was increased from 200mg/l to 1000mg/l. The decrease in corrosion rate is attributed to inhibition of plant extract on the corrosion of mild steel. Inhibition efficiency of Bamboosa vulgaris leaves extract increased with increase in the concentration of its extract. However the corrosion inhibition properties of Bamboosa vulgaris leaves extract is suggested to be as a result of the formation of a protective shielding layer which might have developed around the metal surface under the corrosive medium conditions owing to the organic nature of the Bamboosa vulgaris leaves extract. The formation of the shielding layer is as a result of Bamboosa vulgaris phytochemical molecules adsorption to the metal surface, forming iron (11) complexes with the metal. The adsorption of the plant extract on the metal surface fitted into Langmuir adsorption isotherm, Freundlich adsorption isotherm, and Temkim adsorption isotherm, but best fitted into Langmuir adsorption isotherm. The calculated values of apparent free energy of adsorption are all negative indicating spontaneous adsorption of Bamboosa vulgaris leaves extract on the metal surface.