Gasometric and weight-loss systems was used for studying the corrosion inhibition of magnesium (Mg) in hydrochloric acid by methyl cellulose (MC) polysaccharide as carbohydrate polymer. The two techniques showed a comparable experimental data. The resulting inhibition data of MC on Mg metal surface was found to exhibit both Langmuir and Freundlich isotherms models. Influence of [H⁺] on the rates of corrosion indicates that the rates of corrosion depends on the rate of acid. This finding along with the first order found in [H⁺], suggests that the presence of hydrogen ions should be included at least in the rate-determining step in one of the dissolution pathways of Mg metal in the corrosive medium of HCl. The corrosion rate factors were investigated. Again, the inhibition efficiency increases with increasing the inhibitor concentration and temperature. The inhibition effect of the MC on the magnesium metal surface was confirmed by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) techniques to confirm the extent of corrosion and film formation of MC on the magnesium metal surface. Kinetic parameters were estimated and a suitable corrosion mechanism in good agreement with the kinetic results is suggested and discussed.