In this study, we demonstrate the use of rubber-modified polybenzoxazine (PBZ)/graphene oxide (GO) as a coating to protect carbon steel from corrosion. GO, acting as the nanofiller, is added in increasing amounts to enhance the barrier property of the resulting nanocomposite coatings. Results via immersion in chloride solution coupled with standard electrochemical measurements show that the rubber-modified PBZ is able to protect carbon steel from corrosion attack. Even more, the coatings containing small amounts of GO provided enhanced protective abilities for the carbon steel. By varying the amount of GO, the protective property is tuned and the optimum GO concentration that could offer the most enhanced corrosion resistance property is determined.