This paper investigates the effects of spatial effects of seismic ground motions on the seismic responses of long-span cable-stayed bridges, considering their large range and notable variations in local site conditions. Shaking table tests were conducted on a cable-stayed bridge, and the dynamic responses (acceleration, displacement, and strain) of critical sections of the cable-stayed bridge were compared and analyzed. The results demonstrate the significant influence of spatial effects of ground motion on the dynamic responses of the cable-stayed bridge. Specifically, the analysis reveals that the wave passage effect has the least impact on the dynamic responses of the cable-stayed bridge, followed by the combined effect of the wave passage and coherence, while the combined effects of the wave passage, coherence, and local site conditions exert the largest influence. Taking the main tower as an example, the maximum acceleration, displacement, and strain responses increased by 55.69%, 62.37%, and 67.37%, respectively, when spatial seismic motions incorporating the wave passage effect, coherence effect, and local site effects were considered, as compared to uniform excitation. Consequently, the seismic responses of cable-stayed bridges may be underestimated if only uniform excitation or the wave passage effect is considered. It is therefore imperative to comprehensively account for the effects of wave passage, coherence, and local site conditions of the spatial ground motion in the dynamic response analysis of long-span cable-stayed bridges.