MXene is becoming more and more active in the field of anticorrosion coatings. In this work, Ti₃C₂ nanosheets were modified with dopamine monomer and then introduced into waterborne epoxy coatings (EP). Composite coatings with unmodified Ti₃C₂ nanosheets were also prepared for comparison. Anticorrosion properties of the coatings were evaluated via electrochemical impedance spectroscopy and salt spray tests in detail. Dopamine monomer was readily attached to Ti3C2 nanosheets via chemical bond and saturated at 0.075 mg/mg Ti₃C₂. The modified Ti₃C₂ (D-Ti₃C₂) showed slightly deteriorated dispersibility in water but better dispersibility in waterborne epoxy resin relative to unmodified Ti₃C₂. The impedance modulus of D-Ti₃C₂ coatings achieved four and two orders of magnitude enhancement compared with EP and unmodified Ti₃C₂ coatings, respectively. The addition of D-Ti₃C₂ reduced the water absorption of EP by 80% after a prolonged immersion process. Superior barrier ability and enhanced dispersion of D-Ti₃C₂ nanosheets were responsible for the efficient enhancement of the anticorrosion performance of waterborne epoxy resin coating.