An investigation aimed at assessing the inhibitory efficiency of the arbutus plant extract against the corrosion of carbon steel, in 3% NaCl solution, was carried out using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The plant extract was rich in polyphenols and flavonoids. In order to assess antioxidant activity of this plant extract, 20 ml MeOH solution was prepared and 0.7 mg of DPPH was poured into the solution. The mixture was then stored at +4 °C in dark A certain volume V of the strawberry leaf extract was added to 2 mL test sample of a previously prepared methanolic solution. The reaction time varies according to the chemical nature of antioxidant and depends on its antioxidant power. The results obtained show that the plant extract has an inhibitory efficiency of 90.4% and 92.7%. The EIS results showed maximum inhibitory efficiency (92.4%) at an inhibitor concentration of 100 ppm. The polarization curves indicated that the plant extract is an anodic-type inhibitor. The inhibitory efficiency decreases with the increase in temperature. Thermodynamic parameters were determined and discussed. Adsorption of the plant extract on the carbon steel surface obeyed Temkin, Framkin and El-Awady adsorption isotherms. This paper provides new information on the use of the strawberry (Arbutus unedo L.) plant extract as a green corrosion inhibitor, even in very aggressive alkaline environments. It has not been published elsewhere.