The inhibitive action of 1-cyclohexyl-3-cyclopenta-1,3 dienyl-1,3 diphenyl thiourea (CCDDTU) on corrosion of mild steel in 2M H2SO4 has been studied using weight loss, gasometric measurements, potentiodynamic polarization and impedance studies. The studies clearly indicated that inhibitor reduced the dissolution of mild steel in sulphuric acid by behaving as cathodic inhibitor. The adsorption of this organic molecule on mild steel surface obeyed Temkin's adsorption isotherm. The quantum mechanical analysis proved the inhibition efficiency of the compound calculated from chemical and electrochemical measurements. © 2014 University of Manchester and the authors.