Introduction The effect of Kalmegh leaf extract (KLE) on the corrosion behavior of aluminium in 1 M NaOH solution was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) studies.Results Inhibition efficiency (g%) increased with increasing the concentration of extract and maximum inhibition efficiency observed is 82.24 and 82.45% from EIS and PDP studies, respectively, at higher concentration. Conclusion The adsorption of the inhibitor on aluminium surface was in accordance with the Langmuir adsorption isotherm. Potentiodynamic polarization study showed mixed type inhibition with predominantly cathodic effect. SEM and AFM study was carried out to support the experimental inhibition data.