Background: Benign multicystic mesothelioma is a rare pathology. Few cases are reported in the medical literature and acute presentation is extremely uncommon. Case presentation: We describe an acute clinical presentation of the neoplasm that revealed itself with signs and symptoms attributable to acute appendicitis in a 41-year-old white man. Abdominal echography and computed tomography scans demonstrated the presence of a mass in direct contiguity with cecal fundus, but diagnosis remained unclear. Our patient underwent surgery and complete removal of the neoplasm. Only a definitive histological examination defined the nature of the lesion. No signs of relapse were demonstrated 1 year after the operation. Conclusions: We showed that an acute presentation of a benign neoplasm represents a diagnostic and therapeutic challenge for the surgeon, because of the difficult differential diagnosis that acute presentation can sometimes pose and the trouble that an emergence treatment can imply. Keywords: Acute appendicitis, Multicystic mesothelioma, Peritoneal neoplasm