Phyllanthus niruri L. (Euphorbiaceae) (P. niruri) is a well-known hepatoprotective herbal plant. In the present study, hepatoprotective potential of the protein isolate of P. niruri was investigated against carbon tetrachloride (CCl(4)) induced liver damage in vivo. Protein isolate of P. niruri was intraperitoneally injected in mice either prior to (preventive) or after the induction of toxicity (curative). Levels of different liver marker enzymes in serum and different anti-oxidant enzymes, as well as lipid peroxidation products and glutathione (GSH) in liver homogenates were measured in normal, control (toxicity induced) and protein isolate treated mice. Administration of CCl(4) increased the serum glutamate pyruvate transaminase (GPT) and alkaline phosphatase (ALP) levels of mice sera along with increased lipid peroxidation and reduced levels of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in the liver. Treatment with the protein isolate of P. niruri significantly altered these changes to almost normal. The protein isolate also showed protective properties as was evidenced in histopathological studies. Results suggest that the protein isolate of P. niruri protects liver tissues against oxidative damage and somehow helps stimulating repair mechanism present in liver. It could be used as an effective hepatoprotector against CCl(4) induced liver damage.