<p>Thermal fatigue cracking, wear, and pitting corrosion of Ni–Co alloy coatings on high-speed continuous casting mold copper plates are critical issues limiting their service life. This study fabricated Ni–Co–ZrO₂ nanocomposite coatings on a Cu–0.6Cr–0.1Zr substrate <i>via</i> electrodeposition. The synergistic mechanism between nano-ZrO₂ particles and the alcohol ethoxylate (AEO) dispersant was systematically investigated. The results demonstrate that the synergistic use of an appropriate amount of nano-ZrO₂ (15 g/L) and AEO-7 (0.8 g/L) enabled the fabrication of an optimal coating (ZP-8) with a significantly refined microstructure. Its average grain size was reduced from approximately 500 nm to about 150 nm. This process also induced the formation of a strong (111) texture [RTC(111) = 81.3 pct] and a high density of nano-twins, while markedly lowering the internal stress. Consequently, this coating exhibited outstanding comprehensive properties. Its microhardness and high-temperature yield strength at 400 °C reached 516 HV_0.1 and 479 MPa, respectively, exceeding the peak thermo-mechanical stress level (approximately 382 MPa) under operating conditions at a casting speed of 1.9 m/min. The average coefficient of friction was reduced to 0.537, and the wear rate decreased by 48.6 pct compared to the Ni–Co alloy reference coating without nanoparticle addition (ZC-0). In a 3.5 wt pct NaCl solution, it showed the lowest corrosion current density (0.42 <i>μ</i>A/cm²) and the highest polarization resistance (61.92 kΩ·cm²), indicating significantly enhanced corrosion resistance. The property improvements originate from multiple synergistic strengthening mechanisms, including grain refinement, texture strengthening, dispersion strengthening, nano-twinning, and ZrO₂ transformation toughening. This study provides a theoretical basis for developing high-performance, long-life protective coatings suitable for high-speed continuous casting molds.</p>