Congenital peritoneal encapsulation is a rare entity characterized by an accessory peritoneal membrane that forms during embryonic development. Congenital peritoneal encapsulation is generally asymptomatic but can cause intermittent, colicky abdominal pain related to subacute small bowel obstruction. Diagnosis is made incidentally or upon surgical exploration for chronic abdominal complaints as preoperative imaging is typically nonspecific. We report a case of a 49-year-old male with epigastric abdominal pain, constipation, and superior mesenteric vein thrombosis on imaging. Upon exploratory laparotomy, the small bowel was covered by an accessory peritoneal sac consistent with congenital peritoneal encapsulation. The accessory sac was excised completely, and the patient recovered well. Although rarely causing significant gastrointestinal symptoms, congenital peritoneal encapsulation is an anomaly that requires surgical intervention.