The Inhibition of mild steel corrosion in 5% NaCl solution using 1, 3-diorthotolyl thiourea (DOTU) has been reported by weight loss, electrochemical polarization technique, impedance method and quantum mechanical measurement. It was found that the compound effectively reduces the steel dissolution in the salt water medium. It was also noticed that the mere adsorption of the compound on metal surface follows Temkin's adsorption isotherm. The inhibition efficiency (IE) increases as the inhibitor concentration is increased. Quantum mechanical studies confirm the adsorption of protective layer of inhibitor on mild steel surface. © 2013 University of Manchester and the authors.