Tuberculosis is a curable infective disease which can mimic a malignant tumor. We report on a young woman who presented with abdominal fullness, body weight loss, and microcytic anemia. A pelvic mass and peritoneal lesions were found. The serum CA125 level was high. The initial gynecologic echo and abdominal CT scan revealed bilateral ovarian mass with peritoneal lesions, and malignancy was highly suspected. Diagnostic laparoscopy was performed, and peritoneal tuberculosis was pathologically proven. Combination anti-tuberculosis therapy was prescribed for one year. She was followed up in the outpatient clinic regularly with symptom improvement, body weigh gain, and improvement of anemia. We suggest that in cases of a pelvic mass and peritoneal lesions, with elevation of the serum CA125 level, tuberculosis should always be kept on the list of differential diagnoses. A tissue diagnosis should always be obtained before treatment, regardless of initial image study and laboratory findings.