Breast cancer is the most common type of cancer and leading cause of cancer death in women. This work was aimed at evaluating the potential chemopreventive effect of ethanolic extract of Annona muricata leaves on 7,12-dimethylbenzeneanthracene-induced cell proliferation in the breast tissues of female albino mice. Crude extraction protocol was employed in the preparation of ethanolic extract of Annona muricata leaves. Agarose gel electrophoresis was used to analyze deoxyribonucleic acid (DNAs) extracted from the breast tissues of experimental mice while H and E was used for histological assay. DNA smears obtained from agarose gel electrophoresis suggested a possible DMBA-induced damage which was significantly prevented owing to the effect of the leaf extract of A. muricata leaves. Histological assay revealed the presence of DMBA induced lobular alveolar hyperplasia, fibro adipose stroma,and proliferating sebaceous gland in the histological sections of the breast tissues of treated mice, however, these changes were found to vary in occurrence among the different groups of treated animals. A. muricata could be used as a prophylactic measure against DMBA-induced cell proliferation