Aim of the work- This study aimed to investigate the histological and histochemical changes in the lung tissue of male albino rats post exposure to gamma radiation and the possible therapeutic effect of both olive leaf extract and bone marrow mesenchymal stem cells. Matrerial and methods-The current study was carried out on 40 adult male albino rats (Sprague dawely strain); they were divided equally into 5 groups (C group: control rats; O group : rats treated with olive leaves extract( 15 mg /kg body weight/daily) ; R group: rats exposed to a single dose of gamma-radiation(3 Gy); RO group: rats of this group treated with olive extract 15 mg /kg body weight/daily one week before and one week after irradiation;  RS group: rats of this group irradiated with 3Gy then treated with bone marrow mesenchymal stem cells ( BMSCs)  3×10⁶  cells/ml suspension through caudal vein about 5h post radiation exposure. Histopathological and histochemical changes were studied. Results-Rats exposed to gamma radiation showed numerous histological and histochemical changes, these changes were ameliorated by using either olive leaf extract or bone marrow mesenchymal stem cells. BMSCs showed more obvious therapeutic effect than olive leaf extract.  Conclusion-The present work showed that olive leaf extract or bone marrow mesenchymal stem cells (BMSCs) have lung tissue radiotherapeutic effects against whole body gamma radiation in male albino rats.