Success rate of laparoscopic pyeloplasty for ureteropelvic junction obstruction (UPJO) in children is comparable with open pyeloplasty. Prolonged ileus and injury to adjacent viscera more often occurred in transperitoneal approach; however, longer operation time is noted in retroperitoneal approach. This study presented a hybrid retroperitoneoscopic pyeloplasty (HRP), for congenital UPJO in infants weighing <10 kg. From February 2017 to June 2020, 10 HRP procedures were performed in 9 patients by 1 surgeon. Retroperitoneal dissection of the renal pelvis and the upper third ureter was first performed, followed by extracorporeal suturing for pyeloureterostomy. Mean operative age and body weight were 4.23 ± 3.69 months and 6.18 ± 1.57 kg. Operative, CO2 inflation, and extracorporeal suture time were 147.9 ± 39.5, 40.6 ± 11.2, and 62.9 ± 26.1 minutes, respectively. Surgical outcome was confirmed by renal ultrasound and diuretic renogram. Postoperative follow-up duration was 15.2 ± 7.7 months. Three patients had postoperative febrile urinary tract infection and recovered after antibiotic treatment. In infants or smaller children with UPJO, the HRP procedure may be considered as an effective and minimally invasive alternative with shorter learning curve for inexperienced surgeons.