Abstract— The goal of this study was to determine the effects of genistein on the weight and histological structure of the uterus in adult and postnatal (P22) female albino mice. Adult female mice given 50 mg genistein had a considerable rise in uterine weight and a highly significant increase in endometrial layer thickness if compared with the other groups. While the thickness of the myometrial layer in both genistein groups was significantly increased in comparison with the control, however, treatment with 10mg genistein caused no significant increase in the weight of the uterus as compared to the control group, but caused a significant increase in the endometrial layer thickness compared with the control group. In postnatal females, the thickness of the endometrium layer was significantly increased in the group of 50mg genistein as compared to the other groups. But the thickness of the myometrium layer was significantly decreased due to the effect of 10 mg genistein when compared to the other groups. Histopathological examination of uteri of genistein groups in both experiments demonstrated variable degrees of degenerative tissues ranging from affected uterine wall thicknesses and luminal (circumference and its branches) and caused hyperplasia in both the lining and glandular epithelium, which is associated with connective tissue edema. In conclusion, genistein has a detrimental effect on the anatomy of the uterus in adult and post-natal female mice, interfering with its functions. Keywords- Adult and post- natal albino female mice, Genistein, Histopathology, Phytoestrogen, Uterus.