Preoperative diagnosis of peritoneal tuberculosis is often difficult because of confusion with ovarian cancer. A 56-year-old woman was admitted to our hospital with abdominal fullness. Ascites, prominent bilateral ovaries, and elevated CA-125 were noted. Computed tomography showed thickened peritoneum and strandings in the mesentery and omentum. Exploratory laparotomy was performed under the provisional diagnosis of ovarian cancer, but the final diagnosis was peritoneal tuberculosis. Careful evaluation of bilateral fallopian tubes and ovaries and peritoneum are helpful for correct diagnosis.