<p>Most studies have explored the association between transportation and urban–rural disparity. However, research focusing on the impact of transportation accessibility on these issues has been relatively scarce. This paper contributes to the literature by examining the spatially varying impacts of multiscale accessibility on urban–rural income disparity (URID) in the Qinba mountainous region (<i>QBM</i>) of China. The results further highlight the differing impacts of county-level, prefecture-level, and provincial-level accessibility on URID. The MGWR model confirms that the effects of multiscale accessibility on URID are spatially heterogeneous. Specifically, county-level accessibility has a significantly negative effect on URID. In contrast, the impacts of prefecture-level and provincial-level accessibility are significantly positive in narrowing the URID, leading to a “diffusion effect.” The narrowing effect of prefecture-level and provincial-level accessibility on URID is more pronounced in the eastern and northern parts of <i>QBM</i>, respectively. In the western mountainous areas of <i>QBM</i>, where most counties experience relatively low accessibility and high URID, prioritizing the expansion of connectivity between mountainous and well-developed areas, optimizing the layouts of villages and towns, and improving overall accessibility is essential. The findings suggest that the implementation of accessibility improvements and transport plans should be place-specific, considering the geographical and socio-economic contexts.</p>