Scar-free abdominal wall surgery is a research hotspot in recent years. This study presented surgical skills of transumbilical laparoendoscopic single-site pyeloplasty (LESS-P) for pediatric patients with ureteropelvic junction obstruction (UPJO) and its clinical application. Twenty-four pediatric patients with UPJO had transumbilical LESS-P performed by the same surgeon from June to December 2010. Among them, 16 were males and 8 females aged from 2 to 62 months with average of 14 months. Eighteen patients had obstruction on the left ureteropelvic junction and six on the right. The renal pelvis and ureter were anastomosed using 5-0 absorbable sutures and a double-J ureteric stent was placed through the anastomotic stoma. All operations were successful. None was converted to open surgery and no additional sheath tube or incision besides umbilicus was needed. No intraoperative complications occurred. Ectopic blood vessels were found in two cases during surgery. The mean operative time was 145 min, and the average blood loss about 10 ml. Abdominal drainage tubes were remained for 2-9 days after surgery. The mean postoperative hospital time was 7 days. Two patients had postoperative urinary fistula, which naturally disappeared at 4 and 7 days of postoperation, respectively. Ultrasound and diuretic renal scintigraphy in follow-up found 23 patients had significantly decreased renal pelvis diameter. Although the other one showed no obvious change, but diuretic renography showed significantly improved excretion as indicated by increased glomerular filtration rate from 29 ml/min before surgery to 46 ml/min 6 months after surgery. Pediatric transumbilical LESS-P is not only safe and effective but also can well meet patient's aesthetic desire for scar-free abdominal wall.