A 3-week-old boy presented with repeated episodes of vomiting and constipation. At laparotomy a jejunal diverticulum arising from its antimesenteric border and extending retroperitoneally was found. The narrow neck of diverticulum caused a situation similar to a Richter's hernia. The fundus of diverticulum was attached to the upper pole of left kidney. A retroperitoneal jejunal diverticulum is a new addition to the cause of neonatal intestinal obstruction.