Pseudomyxoma peritonei (PMP) is rare being characterized by intraperitoneal accumulation of mucinous ascites produced by neoplastic cells, mostly originating from a perforated appendiceal adenoma. The clinical signs of the disease are variable, and preoperative diagnosis is often difficult. We describe the clinical case of a 67-year-old patient referred to our unit one month after a left inguinal hernia repair, presenting clinical signs compliant with PMP. Surgical cytoreduction, peritonectomy, appendectomy, and greater omentectomy with perioperative intraperitoneal chemotherapy were performed. The patient was disease free for a 15 month period when he died apparently due to a cardiac event. We advocate that in all cases of gelatinous fluid in a hernia sac PMP must be suspected, thus histological investigation is mandatory as well as abdominal computed tomography (CT) in order to confirm the diagnosis.