Grewia tiliaefolia is commonly used in India and several other countries for its ethnomedical properties. The antioxidant effect of 50% methanol extract of Grewia tiliaefolia bark was investigated by in-vitro and in-vivo methods. The extract exhibited $IC_{50}$ value of $51.40{pm}3.98;{mu}g/ml$ in DPPH assay. In the in vivo experiments, the treatment was given at 250 and 500 mg/kg body weight doses orally for seven days and catalase, SOD, TBA-RS and ascorbic acid levels were estimated. Both the doses caused a significant increase in the levels of catalase in the liver and kidney, and SOD in the liver, kidney and blood serum. A significant decrease in the level of TBARS was also observed. These results suggest potent antioxidant nature of the extract.