The inhibitive action of Dicloxacillin (DCX) on corrosion of mild steel in brine water (5% NaCl) has been studied using weight loss, gasometric measurements, potentiodynamic polarization and impedance studies. The studies clearly indicated that DCX acted as cathodic inhibitor. The adsorption of the compound on mild steel surface obeyed Temkin’s adsorption isotherm. Diffused reflectance spectra and SEM images confirmed the formation of adsorbed film of inhibitor on metal. © 2017 University of Manchester and the authors.