Owing to growth defects, the CrN coating-substrate system may suffer from severe corrosion and wear attack in a marine environment, which limits the coating protection against the 316L substrate. To improve the efficiency, a new approach of fabricating Al2O3/CrN duplex coatings to achieve excellent corrosion and wear performances was provided by sealing the growth defects and extending the deposition time of the CrN layer. The Al2O3/CrN duplex coatings were obtained by multi-arc ion plating system sputter CrN layers combined with sequential atomic layer deposition Al2O3 layers. The morphology and structure of the as-deposited coating were investigated by scanning electron microscopy and x-ray photoelectron spectroscopy. The corrosion performances and tribological properties of the Al2O3/CrN duplex coatings in a seawater environment were investigated. The results showed that the density of the duplex coating decreases as the CrN layer thickness increases. The Al2O3/CrN duplex coatings with a suitable CrN layer thickness exhibited superior corrosion resistance in a seawater environment, which may be ascribed to the Al2O3 layer filling or sealing the partial growth defects of the CrN layer and playing a good barrier role to prevent the infiltration and penetration of corrosive media. Furthermore, the wear rate of the Al2O3/CrN duplex coating was reduced more than 30% compared to the single CrN coating of the same thickness. The good wear resistance of Al2O3/CrN duplex coatings was attributed to the synergistic effect of the dense structure, high wear resistance of the Al2O3 layer, and the supporting effect of the CrN layer as well as the formation of the lubricating component of CaCO3 and Mg(OH)(2) during wear progress.