Two female Yorkshire terrier was referred to Veterinary Medical Teaching Hospital, Seoul National University. In case 1, clinical signs were vomiting, anorexia and weight loss. Cystic intraabdominal mass was identified in radiographic and ultrasonographic examination. In case 2, clinical sign was abdominal distension. In radiographic and ultrasonographic examination, cellular ascites and bilateral intraabdominal masses next to kidneys were observed. Many clusters of glandular epithelial cells with anisocytosis, anisokaryosis, high N:C ratio coarse chromatin and prominent nucleoli were shown in cytologic examination of sanguineous ascites. In all two cases exploratory laparotomy was performed and enlarged ovaries were observed (Rt: 6$ imes$5$ imes$5 cm and Lt: 3$ imes$2$ imes$1 cm in case 1 and 3$ imes$2$ imes$1 cm bilaterally in case 2). After ovariohysterectomy histopathologic examinations were performed. Histopathologically the masses were diagnosed as ovarian adenocarcinoma and ovarian cystadenocarcinoma in case 1 and case 2, respectively. In both dogs no further chemotherapy was carried out. These two dogs had no gross evidence of tumor recurrence at the time of 3 months after tumor resection, but long-term follow-up might be needed.