Impact resistance of structures has become an essential part of construction projects, especially in mountain zones due to the prominent hazard of falling rocks. Some environmental changes, such as deforestation and modifications in landslides, have increased the danger to civil structures and pose a serious threat to the infrastructure and human life. The effect of impact due to landslide falling rocks on reinforced concrete (RC) slabs has been investigated by many researchers, while very few studied the effect of impact loading on prestressed structures. Therefore, the aim of this study is to investigate the behavior of post-tensioned (PT) slabs under impact load. A comparison was made with a traditional (RC) slab having a similar moment capacity. The RC slab was a flat slab with a thickness of 320 mm, while the other two slabs were PT with a thickness of 250 mm. The slabs were subjected to an impact load of 605 Kg dropped freely from 20 m. The load was dropped at the center of gravity for the RC and PT1 slabs. On the other hand, the load was dropped at mid-span of the free edge of the second post-tensioned slab PT2. The tests showed the behavior of the PT slabs under dynamic impact load due to the free falling block, and their different behavior from the RC slab, by comparing displacements, impact force, cracks, and damage type. Also, the results displayed the effect of impact location on the response of PT slabs through analyzing PT1 and PT2 results.