The corrosion inhibition of Pistachio Essential Oils (PEO) on carbon steel in 0.5 M H2SO4 was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results showed that PEO inhibited carbon steel corrosion in a 0.5 M H2SO4 solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor. Potentiodynamic polarization studies suggested that this inhibitor is a mixed type inhibitor with predominance anodic type. Nyquist plots indicated that the addition of inhibitor decreases the double-layer capacitance (Cdl) of the corrosion process depressed semicircles with their centre below real axis. The PEO adsorption on the carbon steel surface followed the Langmuir adsorption isotherm. © 2015 The Authors.