The case is about by a 6-year-old Boston terrier breed dog brought to the Animal Hospital Obstetrics and Gynecology clinic of Fırat University. Clinical complaints including loss of appetite, pain, fever and some discharge for three days were reported. As a result of clinical examinations, a diagnosis of cystic endometrial hyperplasia-pyometra complex (CEH-P) was made. In the treatment protocol, cloprostenol (1st, 3rd, 5th and 7th days), Potassium penicillin G + Procaine penicillin G (7 days), and fluid therapy were administered. Since hematological values did not decrease to within the normal range on the eighth day. Aglepristone (1st, 3rd, 7th and 14th days), cloprostenol (1st, 5th and 8th days), with ceftriaxone disodium (10 days) and liquid electrolyte triple therapy protocol was applied. With this protocol, the amount of discharge increased and the uterine content decreased. After the treatment protocols, ovariohysterectomy operation was performed in order to prevent relapse that may occur due to age and due to nonconsideration to have puppies. In the pathology of the uterus, macroscopically, the uterine serous surface was diffusely hyperemic and edematous, and the mucosa had diffuse nodular cystic areas and hemorrhagic areas up to 0.5 cm. In microscopic findings, the endometrial epithelium showed hyperplasic proliferations. In addition, while cystic dilatation in the endometrial glands and hyperplasia in the gland epithelium were noted, some gland lumens were filled with mononuclear cells and neutrophil leukocytes. In some areas, infiltrating cells reached the myometrium. The overall microscopic lesion was defined as prominent cystic dilatation. As a result, it was concluded that the prostaglandin analogue alone does not provide adequate treatment, and its combined use with antiprogestagen is more successful in the treatment of CEH-P.