The effects of fipronil (FPN) on the liver of rats were studied. Rats (n = 6) were treated with 9.7 mg/kg (1/10 of FPN LD50), and other rats (n = 6) received 120 mg/kg of 10% Uncaria tomentosa extract, while a mixture of 9.7 mg/kg FPN and 120 mg/kg of 10% Uncaria tomentosa extract were administered orally to the rats (n = 6) daily for 6 weeks. Body, hepatic weights, liver enzymes, and lipid profile were determined. Hepatic activities of MDA, TNO, TAC, TNF-α, and IL-6 in liver homogenate were measured. Immunohistochemistry of NF-kB and liver histopathology were performed. Fipronil-treated rats had a significant (P =0.02) lower weight gain. Moreover, relative liver weight was significantly (P = 0.003) increased in FPN-treated rats. Rats administrated with FPN exhibited a significantly (P = 0.02) higher liver enzymes and promoted levels of MDA, TNO,TNF-α, and IL-6 (P < 0.0001) than that in the other groups. Immunostaining of NF-κB was increased (P < 0.0001) in FPNtreated rats. Interestingly, Uncaria tomentosa alone or with FPN decreased the liver immunostaining of NF-κB. In conclusion,FPN produced liver injury through lipid peroxidation and stimulation of NF-κB. However, Uncaria tomentosa combated the oxidative stress and liver damage induced by FPN via inhibition of NF-κB.