Garlic oil (GO) is a natural product that can act as an antioxidant. Recent studies show that GO can act as an antioxidant because it contains several organosulfur compounds which could neutralize free radicals and may increase endogenous antioxidant that protect DNA from the damage induced by genotoxicity, specifically from Sarimukti landfill leachate. Sarimukti landfill leachate is known to be able to damage DNA because it contains heavy metals and some organic compounds that may induce oxidative damage on DNA. This study was aimed to evaluate the protective effect of GO on DNA damage induced by landfill leachate. This study was separated into two section. In first section, male Wistar rats (8-10 weeks, 200-250 gram) were pretreated with GO for 7 days continued co-treatment GO and leachate separated by 2 hours of interlude. In second part, rats were only co-treated with GO and leachate with the same interlude as the first part. In each part, rats were divided into 3 groups treated with GO (20,44.7, 100 mg/kg BW), group treated with vitamin E 50 IU as positive control, and group treated with olive oil as negative control. GO, vitamin E, and olive oil are given by gavage, while leachate (63%) is given through intraperitoneal injection. Protective effects of GO on DNA damage was evaluated using alkali version of comet assay in bone marrow and peripheral blood. GO showed protective effects against DNA damage as indicated by the low level of damage and dose-response relationship between increasing doses of GO and decreasing of DNA damage level, although only significantly different (p <0.05) at the highest dose of GO. The optimum dose for GO is 100 mg / kg BW. The protective effect of the GO also affected bone marrow with better result than peripheral blood. Besides, the pretreatment continued with co-treatment shows higher protection but no significant difference if co-treatment only being applied without pretreatment. As an antioxidant, garlic protects DNA by reducing the level of oxidative stress induced by landfill leachate. The results of this study shows that GO has protective effect on DNA damage induced by landfill leachate.