Water and alcohol extracts were prepared from dried and powdered leaves of Thuja orientalis (T.orientalis). The reducing power, total phenolic content, the 1,1-diphenyl-2-picrylhydrazylscavenging activity, inhibitory effect on Fe (II)-EDTA-H2O2 (Fenton reaction system) inducedDNA damage and inhibitory effect on human red blood cell (RBC) hemolysis were evaluated inthe present study. At a concentration of 200 mg, water and alcohol extracts of T. orientalisinhibited the hydrolysis of DNA by 72.859% and 65.312%, respectively. Water and alcoholextracts of T. orientalis also inhibited 2,2’-Azobis(2-amidinopropane) dihydrochloride inducedRBC hemolysis to the extent of 69.30% and 54.55%, respectively. The reducing power andantioxidative activity of water extract was found to be more than that of alcohol extract. This isattributable to the presence of higher amount of phenolic compounds in water extract. Thepresent results indicate that the T. orientalis extracts are rich sources of natural antioxidants andcan protect DNA and human red blood cells against free radical induced oxidative damage.