Radiotherapy is often used for the treatment of cancer. However, it causes some side effects in patients. This study aimed to determine the hepatoprotective effects of Urtica dioica L. seed-extract (UDSE) in radiation-induced liver injury. Thirty-two male rats were randomly divided into 4 groups (n=8): control(C) group: no action was taken; radiation (R) group: irradiation was administrated at 5Gy single-fraction, radiation with UDSE(R+UDSE) group: irradiation was administrated at 5 Gy single-fraction and animals were fed pellets with 30 mL UDSE/kg; UDSE group: animals were fed pellets with 30 mL UDSE/kg. All of the experiments were performed in all of the groups over 10 days. Malondialdehyde (MDA) and reduced-glutathione (GSH) levels and superoxide-dismutase (SOD), catalase (CAT), glutathione-peroxidase (GSH-Px), aspartate-transaminase (AST), and alanine-aminotransferase (ALT) activities were detennined. Histopathological findings were also evaluated in liver tissues. SOD, CAT and GSH-Px activities and GSH levels in the serum and liver were significantly increased, while MDA levels decreased in the R+UDSE group compared with the R group (P<0.05). Moreover, AST and ALT serum activities in the R+UDSE group were lower than those in the R group (P<0.05). In addition, radiation induced degenerative/necrotic changes in the R group were significantly compensated in the R+UDSE group. The results showed that radiation increased oxidative stress and decreased antioxidant capacity, as well as degeneration in the liver. However, UDSE attenuated these degenerative changes.