Inhibition of carbon steel corrosion in 0.5 M hydrochloric acid solutions by beta-cyclodextrin modified natural chitosan was investigated by weight loss measurement, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The results indicated that the inhibition efficiency increased with the inhibitor concentration at 298 K. The experimental results revealed that beta-CDchitosan (beta-cyclodextrin modified chitosan) was a mixed inhibitor with a maximum achievable inhibition efficiency of 96.02%. Adsorption of beta-CDchitosan was found to follow the Langmuir adsorption isotherm which involved both physisorption and chemisorption. The results of SEM and EDS studies further confirmed the inhibition action of polymer.