This study explores whether improvements to the built environment can promote more active time use among older adults in rural China. Matching a panel of 1,533 observations with infrastructure investment data from Anhui Province, a Difference-in-Difference model was employed. The results show that infrastructure investment in rural areas increased the ratio of active pursuits to passive activities. However, this treatment effect was only observed in leisure activities. Time spent on volunteering rose by 9.58%, while time spent on personal care declined by 10.54%. Meanwhile, exercise time remained stable, though the proportion occurring during evening or night-time hours increased significantly. The findings indicate that improving the built environment encourages more active behavior among older adults. In resource-limited rural areas, such built environment improvements may be effective in addressing physical inactivity among older adults.