This research was performed to study the effect of date palm fruit (Phoenix dactylifera L.) on the 7,12-dimethylbenz (α) anthracene-induced mammary cancer in rats. The effect of feeding the fruit at two maturity stages (“Rutab” and “Tamr”) was compared to that of feeding raw soybean seeds and injection with two drugs, preventive and curative against mammary cancer, i.e., tamoxifien and 17-β-estradiol respectively. For comparison purposes, another group of rats was injected with sesame oil. Eighty three female weanling Sprague-Dawley rats were randomly distributed into the treatment groups. Each group received one of the dietary or drug treatments. Another group of rats that received neither drug nor special dietary treatment served as a positive/carcinogen control group. Still another group was injected with sesame oil, which is the carcinogen vehicle at the time of injecting the carcinogen, to serve as a negative/carcinogen control group. Three weeks after the carcinogen administration, animals were palpated twice per week to record the appearance of any lesion. At the end of the 26-week feeding period, all animals were killed. Palpable lesions, mammary tissue, and associated lymph nodes were removed, fixed, and prepared for histopathological examination. The diets that contained the date palm fruit reduced significantly (P<0.05) the incidence rate of mammary cancer, palpable tumour multiplicity, tumour size and weight compared to the positive/DMBA control group. In conclusion, the date palm fruit (Phoenix dactylifera L.) protected against DMBA-induced mammary cancer in the initiation, promotion, and progression stages of DMBA-induced mammary carcinogenesis. The effect was comparable with that of the two drugs (tamoxifen and 17-β-estradiol). Further research is required to elucidate the possible mechanisms that might have contributed to the preventive effect of this fruit against mammary cancer.