In this study, the inhibition efficiency of two bio-inhibitors to decrease the corrosion rate of carbon steel in acidic solutions is investigated. These green inhibitors contained the protein prepared from the Hyalomma tick and leech extract. Both potentiodynamic polarization and electrochemical impedance spectroscopy measurements were utilized for this research. When the inhibitor concentration increased, the inhibition efficiency increased for both inhibitors; however, adsorption isotherm mechanisms for these inhibitors were different. In addition, the inhibition efficiency for the leech extract was higher than the Hyalomma tick extract in corrosive solutions. This inhibition efficiency range in the H2SO4 solution was about 93-97% based on polarization test results. Changes in corrosion potential showed that molecules adsorption of both bio-inhibitors on steel substrates acted as mixed inhibitors. Calculated ΔGads values for corrosion reactions in the presence of both bio-inhibitors demonstrated that a physical adsorption event has happened on steel substrates. Based on the EIS test results, when the concentration of Hyalomma tick extract increased to 0.06 g/L, the suggested electrical circuits changed due to the formation of a layer of inhibitor molecules on the steel substrate in the HCl solution.