Free radicals are known to play important role in pathophysiology of hepatic disorders and antioxidants are employed along with other chemotherapeutic agents in treatment of such diseases. In search of natural antioxidant, successive extracts of Hypericum (H.) hookerianum (Family: Hypericaceae) were evaluated by in vitro and in vivo methods. Extracts of aerial parts of H. hookerianum were subjected for 1,1-diphenyl 2-picryl hydrazyl radical scavenging activity (DPPH assay), nitric oxide radicals scavenging assay and thiobarbituric acid reactive substances (TBARS) assay. Methanolic extract was found to be more active than other extracts in DPPH and in vitro TBARS assay with $IC_{50}$ at 5.82 ${pm}$ 1.33 ${mu}g/ml$ and 49.78 ${pm}$ 3.79 ${mu}g/ml$ respectively. While petroleum ether extract showed more potentials in scavenging the nitric oxide radicals with $IC_{50}$ 220.97 ${pm}$ 2.69 ${mu}g/ml$. The administration of $CCl_{4}$ to the control animals caused decrease in the level of catalase and superoxide dismutase, together with significant increase in the level of TBARS in liver and kidney. Reversal of these changes towards normal group was observed by administration of H. hookerianum methanolic extract at 50 and 100 mg/kg body weight, while other extracts were found to be less active.