Breast cancer is the most common causing death in women. Tamoxifen, 1-[4-(2-dimethyl-aminoethoxy) phenyl]-1,2-diphenyl-1-butene), is a nonsteroidal antiestrogen breast cancer prevention drug causing liver toxicity. This study was carried out to elucidate the efficacy of Moringa oleifera aqueous extract against carcinogenic effect of Tamoxifen in male rats. 50 male albino rats were divided equally into five groups: control group (I); Moringa oleifera aqueous group (II) of dose (300mg/Kg/day for 6 weeks); group (III) received Tamoxifen (3mg/Kg/3 days for 6 weeks); rats received orally Tamoxifen and Moringa oleifera aqueous extract together for 6 weeks group (IV) and rats pretreated with Moringa oleifera aqueous extract then Tamoxifen with the same dose and period group (V). In group (III) there were elevate in serum activities of ALT, AST, LDH, and serum levels of  TNF-α, IL-1β, Il-10, cholesterol, TG, LDL, HDL, Urea, Creatinine also liver MDA; NO; ATPase. There were decrease in serum Total protein, Albumin and liver antioxidants markers (TAC and GSH) compared to control. In conclusion, oral administration of Moringa oleifera aqueous extract improved the biochemical markers and provided antioxidant activity against the toxicity of Tamoxifen in liver tissues.