Tamoxifen is a widely used adjuvant treatment of breast carcinoma with partial estrogenic agonist effect. This activity may result in a spectrum of proliferative endometrial abnormalities including uterine polyps. We report a 53-year-old woman receiving tamoxifen for previously excised breast lobular carcinoma who presented with vaginal bleeding. Histologic examination of the endometrium revealed typical morphology of tamoxifen-associated polyp with foci of metastatic lobular carcinoma. Metastatic breast carcinoma to tamoxifen-associated polyp has rarely been described in the literature. Pathologists and gynecologists should be aware of this possibility in women who have a history of breast carcinoma and who are receiving tamoxifen. Careful histologic evaluation of the endometrium is crucial.