Seawalls are critical protective engineering structures that safeguard the security of coastal areas. In severe weather conditions, where strong wind and waves coexist, the combined action of wind and waves results in a significant increase in wave overtopping discharge, thereby threatening the safety and stability of coastal regions. This study experimentally investigated the wave overtopping process of seawalls under wind-wave coupling. The experiments simulated the average overtopping discharge and its characteristics under different wind speeds and wave steepness. The study found that the increase in wind speed significantly altered the wave shape and overtopping morphology, particularly when the wind speed reached 9 m/s and 12 m/s, where the nonlinear characteristics of the waves became more pronounced. As wind speed increased from 0 m/s to 12 m/s, the overtopping layer thickness also increased. The impact of relative crest height (Rc/H) and wave steepness (H/L) on overtopping discharge was significant. Under no-wind conditions, overtopping discharge decreased with increasing wave steepness, particularly at smaller relative crest height. In contrast, under wind conditions, the increase in wind speed significantly enhanced overtopping discharge, especially at higher wave steepness, where the overtopping discharge was more sensitive to wind effects.