The objective of the present study was to investigate the bioactive constituent of diethyl ether extract and to determine whether the diethyl ether extract of Lotus peregrinus L. exerts chemoprotected effect by stimulating apoptosis during medroxyprogesterone acetate (MPA)-DMBA mammary carcinogenesis using the expression of the apoptosis-associated proteins Bax and caspases 9; as well as improvement of oxidative status of the mammary tumor tissue. Sixty female wistar rats (52 days old) were divided into four equal groups. Group I (normal group): rats administered distilled water. Group II (carcinogenic group); on day 0, wistar rats were given DMBA (2.5 mg/ rat; orally) followed by second dose DMBA (2.5 mg/ rat; orally) on day 15, 90-day timedrelease pellets containing 25 mg MPA were implanted’ into rats on day 30. Group III (diethyl ether protected), on day 0, wistar rats were given DMBA (2.5 mg/ rat; orally) followed by second dose DMBA (2.5 mg/ rat; orally) on day 15, on day 26 rats were administered diethyl ether (50 mg /kg. b. wt.; orally), 90-day timed-release pellets containing 25 mg MPA were implanted into rats on day 30. Group IV (diethyl ether treated group); given diethyl ether (50 mg /kg. b. wt.; orally) after induction of mammary cancer. Our findings showed the positive treatment of mammary tumor and improved oxidative status of the tissue was evident by increase in the levels of GSH, Catalase and decreased levels of serum MDA levels which in turn is an indicator of reduced oxidative stress of the tissue. Therefore, this study suggests that diethyl ether extract of Lotus peregrinus can be useful for the treatment as well as improvement of oxidative status of the mammary tumor tissue .Also, was more effective in inhibiting DMBA-MPA induced mammary tumors and modulating the expression of apoptosis associated proteins.