Regional integration policies play a crucial role in promoting coordinated regional development. However, it remains unclear whether the polices simultaneously take into account urban–rural integration to achieve a dynamic balance between efficiency and equity. Based on socioeconomic data from 250 cities in China between 2003 and 2019, we used a staggered difference-in-difference method to investigate the impact of the strategy for the integrated development of the Yangtze River Delta (YD integrated development) on integrated urban–rural development. Our results indicate that the YD integrated development effectively promotes integrated urban–rural development and this conclusion holds after conducting various robustness tests and heterogeneity analyses. Additionally, the YD integrated development can facilitate integrated urban–rural development through the following three main pathways: promoting economic growth, improving road transport links, and advancing technological progress. This paper offers new insights for advancing integrated urban–rural development. The next step could involve the further exploration of the connections between external regional integration policies and internal rural reforms, which will contribute to expediting the establishment of an integrated urban–rural pattern.