Pneumoperitoneum, free intra-abdominal air, usually results from the perforation of a hollow viscous. In approximately 10% of cases, however, pneumoperitoneum is not caused by gastrointestinal perforation. These cases of "spontaneous pneumoperitoneum" generally follow more benign course and may not require surgical intervention. Examples include cardiopulmonary resuscitation (CPR), malrotation, mechanical ventilator support, gynecologic manipulation, blunt abdominal trauma, and chronic intestinal pseudoobstruction in infancy (Sieber syndrome). But, it is extremely rare of spontaneous pneumoperitoneum secondary to idiopathic intestinal pseudoobstruction in adult. We herein report a patient with chronic idiopathic intestinal pseudoobstruction who developed a pneumoperitoneum.