Purpose of investigation: The effects of tamoxifen on lipid peroxidation and oxidant-antioxidant balance in an animal model were studied. Methods: Twelve female adult rats were divided into two groups and DMSO and tamoxifen dissolved in DMSO were administered. Tissues taken from the brain, liver and ovary of rats were dissected. MDA, nitrite, nitrate levels and plasma LDL oxidation in brain, ovary and liver tissues were measured and compared. Results: Induced LDL MDA levels were significantly lower in the tamoxifen group (p = 0.009). MDA levels in the liver were significantly lower in the tamoxifen group whereas nitrite levels were found significantly higher (p < 0.05). Brain and ovarian tissues demonstrated no significant difference with respect to MDA, nitrite and nitrate levels. Conclusion: Tamoxifen has no negative effects on lipid peroxidation in an animal model.