A 45-year-old woman underwent endoscopic transgastric necrosectomy for walled-off necrosis after acute pancreatitis at 36 weeks gestation. After recovery, she underwent laparoscopic cholecystectomy (LC) for cholecystolithiasis, which might have been the cause of pancreatitis. Abdominal CT revealed an abdominal tumor measuring 46mm in diameter one year after LC. We performed laparoscopic resection of the tumor for diagnosis and treatment. Histopathologically, the tumor was diagnosed as a desmoid tumor occurring in the mesentery of the small intestine. Desmoid tumor is a rare, clinically borderline tumor, that can recur locally and grows invasively. Herein, we report a case of laparoscopic surgery for an intra-abdominal desmoid tumor in the mesentery of the small intestine that was difficult to definitively diagnose preoperatively.