Background: Exposure to ionizing radiation is inevitable. Using of low-level laser therapy (LLLT) stimulates tissue repair and reduces inflammation. The objective of the present study aimed at evaluating the therapeutic efficacy of Helium-Neon (He-Ne) laser in stimulating the reparative processes in the liver of mice after whole body gamma-irradiation (WBγ-I). Materials and Methods: Two hundred and sixty four female mice were divided into 6 groups: Control, Laser irradiated,  One shot gamma irradiated group, One shot + laser irradiated, Cumulative gamma irradiated and Cumulative + laser irradiated. Ionizing radiation was performed using a Cesium-137 source. Two modes of exposure were used, 1- Mice were irradiated with a single shot sublethal dose of 5 Gy. 2- The same dose was given in fractionated mode daily installations of 1 Gy. Laser treatment was carried out using a computerized scanner emitting He-Ne (CW). The assessment of serum transferases (AST & ALT) was performed along with histopathological (HP) assessment of liver biopsies.  Results: There was a significant increase in serum transaminases above the control levels in gamma irradiated groups. Laser therapy of these groups was accompanied by a significant decrease in the elevated levels of transaminases. HP changes in the liver of the shot gamma-irradiated group showed that the main brunt  of damage was on the liver cells. Meanwhile, in the cumulative gamma-irradiated group the main brunt was on the vascular system including the central veins and the portal blood vessels. Conclusion: It could be concluded that mice exposed to WBγ-I suffered from aggravated HP changes in the liver tissues accompanied by disturbances in the level of liver enzymes. These undesirable alterations were ameliorated by the treatment of the experimental mice by He-Ne laser before being irreversibly damaged.