Malignant peritoneal mesothelioma is a rare tumor arising from the mesothelial cells of this serosal membrane. The authors report a case of a female patient referred to our hospital for ascites of unknown etiology. As all the exams requested were negative, the patient underwent a diagnostic laparoscopy with biopsies of multiple peritoneal nodules. Histologic examination confirmed the diagnosis of malignant peritoneal mesothelioma. A cytoreductive surgery in combination with hyperthermic intraperitoneal chemotherapy was performed. After four months of the procedure the patient remains asymptomatic.