A 37-year-old woman was admitted to our hospital for a detailed examination of ascites and a lower abdominal mass. Abdominal CT and MRI showed pleural effusion, ascites, a tumor in the descending colon, and a right ovarian tumor. The patient was diagnosed with descending colon cancer by total colonoscopy. Resection of the descending colon and right oophorectomy were performed under a preoperative diagnosis of synchronous right ovarian metastasis from the descending colon cancer or the primary right ovarian tumor. A diagnosis of pseudo-Meigs syndrome due to synchronous ovarian metastasis from the descending colon cancer was made, based on the right ovarian tumor being immunohistochemically positive for CDX2 and disappearance of pleural effusion and ascites after surgery. Postoperative chemotherapy was performed for 36 months and the patient is alive 70 months after surgery without recurrence.