Ni-Co alloy-based nanocomposite coatings are widely used in the engineering field due to their excellent physical and chemical properties. The co-deposition of Al₂O₃-reinforced Ni-Co alloy was successfully achieved using ultrasonic-assisted jet electrodeposition. The effects of ultrasonic power and Al₂O₃ concentration on deposition morphology, surface roughness, adhesion, microhardness, abrasion resistance and self-corrosion properties of Ni-Co coatings were systematically investigated. A favorable Al₂O₃ concentration of approximately 3 g/L in the electrolyte and an ultrasonic power density of 8 W cm⁻² were found to result in improved micro-hardness, adhesion, wear resistance, corrosion resistance, and the highest Al₂O₃ incorporation within the tested range. Under these conditions, the coating exhibited a micro-hardness of 623 HV, an adhesion strength of 36.8 N, a wear track width of 346.8 μm, and a corrosion current density of 5.20 μA cm⁻², indicating excellent comprehensive properties. This study provides valuable insights for the development of environmentally friendly industrial alternatives to conventional hard chromium coatings and demonstrates promising potential for applications in marine engineering.