The influence of Isopropyl thiourea (ISP T) on corrosion and hydrogen permeati on through mild steel in 0.5M H 2SO 4 and 1M HCl has been studied usi ng wei ght l oss measurements and various electrochemical techniques. Isopropyl thiourea (ISPT) is found to be m ore inhibitive in H 2SO 4 than in HCl. Potentiodynamic polarization studies clearly prove the fact that this com pound behaves as a mixed inhibitor; but predominantly as a cathodic inhibitor. Hydrogen permeation studies and AC impedance measurements also indicate an improved perform ance of the compound in H 2SO 4. The adsorption of this compound on the mild steel surface obeys Temkin's adsorption isotherm.