An aqueous extract of Sida acuta leaves (SAL) was prepared and its influence on corrosion inhibition of aluminium in 1N NaOH solution was studied using chemical and electrochemical methods. It was found that the inhibition efficiency increases with the increasing the concentration of Sida acuta extract upto 900ppm. Electrochemical measurements revealed that SAL extract acts as a mixed type inhibitor. Adsorption of SAL extract was found to follow Langmuir adsorption isotherm. The results obtained from chemical and electrochemical measurements were in good agreement. The protective film formed on the surface of aluminium by the adsorption of water-soluble chemical constituents of SAL extract was confirmed by using scanning electron microscopy studies. These results were supported by kinetic and thermodynamic parameters obtained from weight loss data at various temperatures studied.