A 69-year-old female patient visited the previous hospital with anorexia and vomiting. She had weight loss and emaciation and was admitted to the hospital with a duodenal stenosis diagnosis due to superior mesenteric artery syndrome by computed tomography (CT). Conservative treatment with nutritional therapy was performed, but with no improvement;thus, the patient was referred to our hospital. We re-examined the patient to determine the cause of her disease. CT and magnetic resonance imaging findings revealed peritoneal thickening of the pelvic floor, suggesting malignant disease such as peritoneal dissemination. Therefore, we performed diagnostic laparoscopy and harvested peritoneal tissue. She was diagnosed with primary peritoneal carcinoma by histopathological examination and immunohistochemical staining techniques. Thereafter, she underwent chemotherapy for primary peritoneal cancer at the gynecology department of our hospital but died of the primary disease. Primary peritoneal cancer is frequently diagnosed by abdominal distention and abdominal pain due to ascites accumulation. We report this case because of the rarity of primary peritoneal cancer triggered by duodenal stricture.