Pseudomyxoma peritonei (PMP) is a rare clinical condition defined as extensive intraperitoneal spread of mucus associated with a variety of mucinous tumors. Although appendix has usually been implicated as the primary site, some reports found no cause. This case also describes a PMP with no identifiable primary site. A 52-year-old male presented with an abdominal distension evolving for 3 months associated with diffuse abdominal pain, imaging techniques objective intra peritoneal mucoid materials with septated ascites but it failed to identify the primary site. Exploratory laparotomy with Biopsy confirmed PMP but also failed to found the original site.