An attempt was made to synthesize newer coumarin substituted derivatives of benzothiazole and they were evaluated for antioxidant activity by DPPH radical scavenging activity. The test compound SC-7 showed good in-vitro antioxidant activity. The same compound was selected for in-vivo antioxidant studies by administering different doses in Ehrlich Ascites Carcinoma (EAC) treated mice. It reduced the levels of lipid peroxidation and increased the GST contents as well as CAT levels in EAC induced mice. The present study revealed that newly synthesized coumarin substituted benzothiazole derivatives showed significant antioxidant activity in EAC bearing mice.