The current research work was designed to investigate the protective effects of white button mushroom (Agaricus bisporus) against 7,12-dimethylbenz[a]anthracene (DMBA)-induced breast cancer. Breast cancer was induced in rats by the administration of a single dose of 50 mg/kg DMBA via gavage. The rats were divided into four groups: G1 (negative control group), G2 (positive control group), G3 (rats receiving mushroom extract), and G4 (rats administered with doxorubicin). The mushroom extract significantly (p < .001) improved the activity of antioxidant enzymes in carcinogenic rats. Moreover, the mushroom extract also prevented the increase in the concentration of tumor biomarkers that are CEA, CA 15.3, and CRP in experimental rats. Liver function enzymes were also raised in G2 and G4 compared with G3. Besides, the RBCs and Hb were also reduced significantly in G4 while in G3. The mushroom extract effectively controlled the level of RBCs and Hb. An improvement in lipid profile was also measured in mushroom extract receiving rats. Conclusively, the mushroom extract alleviated DMBA-induced breast cancer potentially via improving antioxidants, reducing lipid peroxidation, and decreasing tumor biomarkers. PRACTICAL APPLICATIONS: The present research study examined the antitumor potential of white button mushroom. The mushroom effectively prevented the increase in tumor biomarkers, reduction in antioxidant enzymes, and increase in lipid peroxidation in rats with DMBA-induced breast cancer. The mushroom can be used as a potential source to prevent breast cancer and further research can be conducted to explore its anticancer mechanisms.