Normal tissue damage following radiotherapy (RT) is still a major problem in cancer treatment. So, the current work aimed at exploring the possible role of locally injected bone marrow derived mesenchymal stem cells (BM-MSCs) in ameliorating the side effects of ionizing radiation on the normal rat's tongue. The irradiated group received a single 10GY irradiation dose to the head and neck region. While in the treated group, the tongue was injected by 0.25ml BM-MSCs immediately following irradiation. Histologically, BM-MSCs-treated rats showed an apparent improvement in the epithelial layer thickness, basal layer cellularity, lingual muscles and the acini of von Ebner salivary glands. Besides,immunohistochemical examination revealed increased expression of PCNA and VEGF in the BM-MSCs-treated rats. Thus, BM-MSCs treatment reduced the severity of RT-induced side effects on normal tissues.