Objectives: Polyphenols are vital micronutrients, in our diet, which have a role in the prevention of progressive cancer and cardiovascular diseases developing. The main objective of this research was to evaluate the hemopreventive effects of some polyphenols of Phoenix dactylifera pits on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary cancer of female albino rats.Methods: The phenolics of P. dactylifera pits (Zahidi cultivar) were prepared by successive steps; extraction by ethanol:methanol:HCl:H2O, adsorption chromatography using a silica gel column and preparative high performers chromatography. The cytotoxic activity of the phenolics was detected against human breast cancer cell line (MCF-7). The acetone phenolic fraction, 50 female albino rats, and DMBA carcinogen were used to study the preventive effects.Results: The acetone phenolic fraction contained considerable amounts of the total phenolics and having antioxidant activity, which inhibit cancer cell line MCF-7 growth, and the inhibitory concentration 50% of cells (IC50) at 24 hrs was 202 μg/ml for MCF-7 and 480 μg/ml for WRL-68. The purified phenolic compounds may be related to genistein and quercetin derivatives that inhibited MCF-7 cell line growth and IC50 were 1030 and 203.9 μg/ml, respectively, compared with negligible effects on normal cell line. The acetone phenolic fraction prevented mammary cancer formation in the DMBA-induced rat model.Conclusions: The phenolics of date palm had chemopreventive effects against DMBA-induced mammary cancer, and they required further research to clarify the possible mechanisms that might have contributed to the preventive effects against mammary cancer.