The inhibition effect of Cytisine derivative namely [ N-( 3- Methylthio-5-acetamido-1,2,4-thiadiazolyl ) cytisine ] on mild steel in 1M H2SO4 has been studied by using weight loss, electrochemical polarization and scanning electron microscopic (SEM) techniques. It has been concluded that percentage inhibition increases with increase in concentration of inhibitor. The adsorption of [ N-( 3- Methylthio-5-acetamido-1,2,4-thiadiazolyl ) cytisine ] on mild steel surface in 1M H2SO4 obeys Langumir adsorption isotherm, surface analysis studies are carried out to establish the mechanism of corrosion inhibition. The polarization data indicate that this compound act as very good cathodic inhibitors for mild steel in 1M H2SO4 and its inhibition efficiency increases with concentration and the highest value obtained is around 92%.