We report a case of malignant peritoneal mesothelioma (MPM) in a 31-year-old male with history of cerebral palsy, hydrocephalus, and ventriculoperitoneal shunt (VPS) placed since infancy. He presented with fever, abdominal pain and distension. Computed tomography scan revealed a thick-walled rim-enhancing fluid collection, interpreted as pseudocyst. Intraoperatively, diffuse nodular peritoneal thickening with adhesions was demonstrated. The resection specimen consisted of multiple membranous fragments displaying firm nodules. Microscopic examination revealed a tumefactive malignant-appearing epithelioid proliferation involving the peritoneum, focally invading the underlying fat. Immunohistochemically, the tumor cells expressed keratin AE1/AE3, CK7, CK5/6, Calretinin, WT1 and D2-40, and were negative for CEA and MOC31. The findings were consistent with MPM, epithelioid type. The patient's condition continued to decline with increasing abdominal distension during the month following the original diagnosis. While atypical mesothelial hyperplasia has been described in association with long standing VPS, well-documented cases of MPM have not been previously reported in such context.