The corrosion inhibition of iron in HCl, HClO 4, H 2SO 4 and H 3PO 4 solutions (1M for each) by cefatrexyl has been studied by polarization resistance ( R p) and electrochemical impedance spectroscopy (EIS) at the corrosion potential. The results obtained at 30 °C revealed that cefatrexyl acts as a weak inhibitor in HCl solution while it shows excellent inhibition performance in the remaining acids. Adsorption of cefatrexyl in HCl solution obeys Langmuir’s isotherm with a very low value of the free energy of adsorption Δ G ads ∘ (physisorption) while its adsorption in the other acids follows Temkin’s isotherm with very high negative values of Δ G ads ∘ (chemisorption). Data obtained from EIS measurements were analyzed to model the corrosion inhibition process through appropriate equivalent circuit models. The calculated values of the apparent activation energy ( E a) and the pre-exponential factor (λ) indicate that cefatrexyl blocks nearly the whole active centers of iron surface in H 3PO 4 solution even at elevated temperatures. The inhibition mechanism of cefatrexyl was discussed.