In this research, the effects of fresh and oxidized MXene on the surface, adhesion, and corrosion-resistant properties of waterborne epoxy coatings are considered. The oxidized MXene is prepared through storage of fresh MXene nanosheets in an open vial for 1 month. The results confirm that the waterborne epoxy coating loaded with silane functionalized fresh MXene nanosheets (epoxy/F-MXene) has significantly higher barrier performance and anti-corrosion behavior than the sample modified with silane functionalized oxidized MXene nanosheets (epoxy/F-O-MXene). Indeed, the F-MXene nanosheets (with defect-free and large two dimensional morphology) are able to effectively inhibit the path of corrosive media as well as increment the epoxy matrix compactness compared to the F-O-MXene (with broken nanosheet morphology composed of TiO₂ nanoparticles) due to rapid oxidation of the MXene nanosheets in the environment. Besides, the epoxy/F-MXene nanocomposite coating has slightly higher water contact angle and adhesion strength to the metallic substrate compared to the epoxy/F-O-MXene. The results of this research clearly reveal the importance of preventing MXene oxidation before application as nanofiller in the polymer coatings.