Malignant mesothelioma is a neoplasm which tends to develop along serosal surfaces, such as the pleura and peritoneum. We report a rare case of malignant retroperitoneal mesothelioma in a 27-year-old woman. The patient was admitted with a chief compliant of intermittent high fever once a month, and left retroperitoneal tumor was detected by dynamic abdominal computed tomography. Since an adrenal tumor was suspected, laparoscopic tumor extirpation was performed. Immunohistochemically tumor cells were positive for calretinin and thrombomodulin, but negative for carcinoembryonic antigen (CEA) and Ber-Ep4. Based on these findings, primary malignant retroperitoneal mesothelioma was diagnosed.