This study investigated the corrosion resistance of graphene/waterborne epoxy composite coatings in CO2-satarated NaCl solution. The coatings were prepared by dispersing graphene in waterborne epoxy with the addition of carboxymethylcellulose sodium. The structure and composition of the coatings were characterized by SEM, TEM, FTIR and Raman spectroscopies. The corrosion resistance of the composite coatings was investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Composite coatings with more uniform surfaces and far fewer defects than blank waterborne epoxy coatings were obtained on 1020 steel. The 0.5 wt% graphene/waterborne epoxy composite coating exhibited much lower corrosion rate and provided better water resistance properties and long-term protection than those of the blank epoxy coating in CO2-satarated NaCl solution. This was attributed to the distribution of graphene inside the composite coating that retarded the diffusion of iron ions and thus the anodic reaction.