The current report describes an unusual presentation of uterine endometrial polyp with severe hemorrhage and cystic endometrial hyperplasia-pyometra complex in a 9.5-year-old female Doberman Pinscher. The dog presented with a 2-day history of bloody discharge from the vulva and an enlarged abdomen. The postmortem examination revealed a markedly distended right uterine horn with a large pedunculated mass (17 cm x 9 cm x 4 cm) and blood. Based on the histological findings, the diagnosis of uterine endometrial polyp was made.