Vasicine compound is the principal alkaloid found in Adhatoda vasica which belong to the family of anthracite, contains vasicine, vasicinone and deoxyvasicine .The alkaloid present in the plant gives expectorant activity, antispasmodic, antiseptic and anthelmintic properties, but not uses as corrosion inhibitor. Hence, in the present study mainly focused on the isolation ,characterization and inhibition effect of vasicine alkaloid from adhatoda vasica. Alkaloids are extracted with ethanol, quantified and identified by reactions and proved using TLC, HPLC, FT-IR and H1NMR and used as corrosion inhibitor. The inhibition of vasicine on mild steel corrosion in 1 N HCl was carried out by weight loss, polarization and impedance methods. Weight loss studies indicated that the inhibition efficiency was found to be increased with increase in the concentration of inhibitor. Polarization studies revealed that the inhibitor act as mixed type inhibitor. AC impedance method indicated that the charge transfer resistance was found to be increased with increase in concentration. The adsorption of inhibitor follows Langmuir adsorption isotherm to gain information about the inhibitive action mechanism. The optimum inhibition efficiency 99 % was obtained for 800 ppm of vaccine at 303 K